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INTERNATIONAL CHEMICAL SERIES 
H. P. TALBOT, Ph. D., Consulting Editor 



TECHNICAL 
GAS AND FUEL ANALYSIS 



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McGraw-Hill Book Company 

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Electrical World The Engineering and Mining Journal 
Engineering Record Engineering News 

Railway Age G azette American Machinist 

Signal ELngin<?<?r American Engineer 

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TECHNICAL 
GAS AND FUEL ANALYSTS 



BY 

ALFRED H. WHITE 

PROFESSOR OF CHEMICAL ENGINEERING, UNIVERSITY OF MICHIGAN 



First Edition 
Second Impression — Corrected 



McGRAW-HILL BOOK COMPANY, Inc. 
239 WEST 39TH STREET, NEW YORK 

6 BOUVERIE STREET, LONDON, E. C. 
1913 



T 7 31.1 
.VI 5 



Copyright, 1913, by the 
McGraw-Hill Book Company, Inc. 




M-WII 



THE. MAPLE . PRESS. YORK. PA 



PREFACE 

With the increased demand for the economic utilization of 
fuels has come an increased necessity for accuracy in testing 
both the raw fuel and the manner of its utilization. Our knowl- 
edge has recently been greatly extended by the investigations 
conducted by the Committee on Calorimetry of the American 
Gas Institute, the International Photometric Commission, the 
Joint Committee on Coal Analysis of the American Chemical 
Society and the Society for Testing Materials, the Bureau of 
Mines and the Bureau of Standards. 

The author has aimed to present the conclusions of these 
committees and also to indicate where there has been marked 
dissent from them. He desires to express his especial appre- 
ciation to Professor O. L. Kowalke of the University of Wis- 
consin for his courtesy in revising the chapter on Determination 
of Heating Value of Gas; to Professor S. W. Parr of the Uni- 
versity of Illinois for suggestions on Calorimetry and Chemical 
Analysis of Coal; and to Dr. H. C. Dickinson of the Bureau 
of Standards for his suggestions on Calorimetry. 

Ann Arbor, Michigan, 
August, 1913. 



CONTENTS 

Page 

Preface v 

CHAPTER I 

Sampling and Storage of Gases 1 

Difficulties involved— The problem of a fair sample — Materials 
for sampling tubes — Types of sampling tubes and their use — 
Aspirators — Solubility of gases in water — Saturating water in 
sampling tanks — Collecting an average sample representative of a 
definite period — Collecting a representative instantaneous sample 
— Storing gas samples. 

CHAPTER II 

General Methods of Technical Gas Analysis 14 

Introduction — General method — The gas burette — Care of stop- 
cock — Saturating the water of the burette — Drawing the sample 
of gas into the burette — Measuring a gas volume — Calibration 
of a gas burette — Connecting the burette and pipette — Details 
of a simple gas analysis — Accuracy of the analysis. 

CHAPTER III 

Absorption Methods for Carbon Dioxide, Unsaturated Hydro- 
carbons, Oxygen, Carbon Monoxide and Hydrogen .... 28 
Carbon dioxide — Unsaturated hydrocarbons — Oxygen by phos- 
phorus — Oxygen by alkaline pyrogallate — Other reagents for oxygen 
— Carbon monoxide — Absorption of hydrogen — General scheme of 
analysis. 

CHAPTER IV 

Explosion and Combustion Methods for Hydrogen, Methane, 

Ethane and Carbon Monoxide 41 

Available methods — Apparatus for explosion analysis — Manipula- 
tion in explosion analysis — Oxidation of nitrogen as a source of 
error — Accuracy of explosion methods — Hydrogen by explosion — 
Hydrogen and methane by explosion — Carbon monoxide, hydrogen 
and methane by explosion — Quiet combustion of a mixture of 
oxygen and combustible gas — Fractional combustion with palla- 
dinised asbestos — Fractional combustion with copper oxide — 
Nitrogen — Form of record of gas analysis. 

vii 



viii CONTENTS 

CHAPTER V 

Page 

Vabious Types of Appabatus for Technical Gas Analysis ... 61 
Introduction — Schlosing and Rolland's apparatus — Orsat's appa- 
ratus — Bunte's burette — Chollar tubes. 

CHAPTER VI 

Exact Gas Analysis 70 

Historical — General methods — Corrections for temperature and 
pressure — Description of gas burettes — The bulbed gas burette 
for exact analysis — Manipulation of gas burette for exact analysis 
— Calibration of burette — Absorption methods in exact gas analysis 
— Carbon dioxide — Unsaturated hydrocarbons — Oxygen — Carbon 
monoxide — Hydrogen — Methane — Nitrogen. 

CHAPTER VII 

Heating Value of Gas 87 

Introduction — Continuous flow calorimeters — Wet gas meters — 
Corrections for temperature and pressure — Control of the water — 
Measurement of temperature — Measurement of mass of water — 
Junkers' calorimeter — Preliminaries of a test — Description of a 
test — Calculation of results — Gross and net heat values — Accuracy 
of method — Determination of humidity of air — Non-continuous 
water heating calorimeters — Automatic and recording gas calori- 
meters — Calculation of heating value from chemical composition. 

CHAPTER VIII 

Candle-power of Illuminating Gas 113 

Introduction — Method of rating candle-power — The bar photo- 
meter- — Standard light — Photometric units — Standard candles — 
The Hefner lamp — The Pentane lamp — Secondary standards of 
light — Standard gas burners — The Bunsen and Leeson photometric 
screens — The Lummer Brodhun photometric screen — The flicker 
photometer — The gas meter — The photometer bench and its equip- 
ment — Details of a test — Illustration of calculation — The photo- 
meter room — Jet photometers — Accuracy of photometric work. 

CHAPTER IX 

Estimation of Suspended Particles in Gas 133 

Introduction — The distribution of particles in the cross-section of 
a straight main — Mean velocity in the cross-section of a gas main — 
Influence of bends in a main — Yelocity of gas in a sampling tube — 
The filtering medium — Estimation of suspended tar and water — 
Electrical precipitation of suspended particles. 



CONTENTS lx 

CHAPTER X 

Page 

Chimney Gases . 139 

Introduction — Formation of carbon dioxide — Effect of hydrogen 
of coal on composition of chimney gases — Carbon monoxide and 
products of incomplete combustion — Volume of air and of chimney 
gases — Loss of heat in chimney gases — Interpretation of analysis 
of chimney gases. 

CHAPTER XI 

Producer Gas 149 

Formation of producer gas — Sampling producer gas — Analysis 
of producer gas — Interpretation of analysis — Heating value of 
producer gas — Volume of producer gas — Efficiency of a gas 
producer. 

CHAPTER XII 

Illuminating Gas and Natural Gas . 156 

Introduction — Sampling — General scheme of analysis — Chemical 
composition of illuminating gas — Benzene — Hydrogen sulphide — 
Total sulphur compounds — Napthalene — Ammonia — Cyanogen — 
Specific gravity — Natural gas. 

CHAPTER XIII 

Liquid Fuels 174 

Introduction — Sampling — Heating value — Specific gravity — Mois- 
ture — Proximate analysis — Suspended solids — Flash point. 

CHAPTER XIV 

Sampling Coal 181 

General consideration — A scoopful as a sample — Influence of 
lumps of slate — Taking a sample — Mine sampling — Preparation 
of sample — Preservation of sample — Usual accuracy of sampling — 
Reliability of samples. 

CHAPTER XV 

The Chemical Analysis of Coal 193 

Introduction — Proximate analysis — Preliminary examination of 
sample — Air-drying — Grinding and preserving the sample for 
analysis — Moisture — Volatile matter — Ash — Fixed carbon — Sul- 
phur — Ultimate analysis — Carbon and hydrogen — Nitrogen — 
Phosphorus — Oxygen — Methods of reporting analyses — Accuracy 
of results — Slate and pyrites. 



x CONTENTS 

CHAPTER XVI 

Page 

Heating Value of Coal by the Bomb Calorimeter 214 

General methods of determining heating value — The bomb calori- 
meter — Details of the bomb calorimeter — Thermometers — Prepa- 
ration of sample — Manipulation of bomb calorimeter — Thermom- 
eter corrections — Radiation corrections — Corrections for oxida- 
tion of nitrogen — Corrections due to oxidation of sulphur — 
Correction due to combustion of iron wire — Reduction to constant 
pressure — Water value of calorimeter — Accuracy of results — 
Gross and net heating values. 

CHAPTER XVII 

Heating Value of Coal by the Parr Calorimeter and Other 

Methods 238 

Introduction — Combustion in a stream of oxygen — The Thompson 
calorimeter — The Parr calorimeter — Preparation of Parr calori- 
meter — Care of sodium peroxide — Operation of Parr calorimeter — 
Corrections to be applied with Parr calorimeter — Accuracy of Parr 
calorimeter — Calculation of heating value from chemical analysis. 

Index 257 



TECHNICAL 
GAS AND FUEL ANALYSIS 

CHAPTER I 
SAMPLING AND STORAGE OF GASES 

1. Difficulties Involved. — The problem of obtaining a repre- 
sentative sample of a gas for analysis presents in many cases 
more difficulties than the analysis itself. If the gas flowing 
through a main were of perfectly uniform composition throughout 
its cross-section and also throughout its length the problem would 
simplify itself to the introduction of a tube through which a por- 
tion of gas might be removed for analysis. The proposition 
becomes at once more complicated when it is necessary to sample 
gases which have not passed through any adequate mixing chamber 
and which usually travel through the main or flue in pulsations 
of widely varying composition. Ocular evidence of this condition 
is afforded by a glance at the average smoke stack with its pulsing 
billows of smoke. If it is desired to determine not only the com- 
position of the fixed gases but also the amounts of suspended 
solids, tar particles, water globules, etc., the problem becomes 
one of great complexity, capable frequently of only partial 
solution. This question is discussed separately in Chapter IX. 

2. The Problem of a Fair Sample. — Gases should be sampled 
as close as possible to the point of the reactions which are to be 
studied, thus minimizing errors due to leakage of air or gas, 
deposition of solids or secondary reactions. Gases travel through 
straight pipes in an irregular succession of waves of rather a 
spiral form, the velocity being greatest at the center of the pipe 
and least next to the walls. The shape of the wave is altered by 
every bend, branch or other change in the pipe and the point of 
maximum velocity is also shifted. The temperature of gases 
from hot furnaces also varies throughout the cross-section of the 

1 



2 GAS AND FUEL ANALYSIS 

conducting pipe, being usually hottest where the velocity is 
greatest and coldest next to the walls and in dead bends. 

It is in general advisable to sample from a point of approxi- 
mately average velocity and temperature, but it is not possible to 
find a single point from which a truly representative instantaneous 
sample can be drawn. It is necessary to extend the sampling 
period over a time which will on the theory of probabilities allow 
so great a series of gas waves to pass the sampling tube that the 
resulting sample will be truly representative. A small volume of 
gas can therefore only be considered a representative sample 
when it has been drawn from a practically homogeneous mass of 
gas — a condition which is rather closely fulfilled in illuminating 
gas which has been purified and further made uniform through 
mixing and diffusion in a large gas holder. The condition is not 
fulfilled in producer or chimney gases. 

No fixed time can be set as the most desirable for a single gas 
sample. If the sample is being taken from chimney gases which 
are supposed to be the same from one hour to another, the sam- 
pling process may very well extend over one hour or six hours. 
The longer the period the more nearly will the sample be an 
average one. The same thing holds true for illuminating gas 
coming from a holder, but it would not hold true for producer gas 
from a single producer nor for illuminating gas from a single re- 
tort, for these gases vary continuously in composition, each fresh 
charge of coal commencing a new cycle. When dealing with gases 
of this sort it is necessary to start and stop the sampling with refer- 
ence to some definite point in the cycle. A truly proportional 
sample of a constantly varying gas cannot be obtained without 
rather elaborate precautions. 

3. Materials for Sampling Tubes. — Sampling tubes must be 
of a material which will not react with the gases and change 
their chemical composition. Iron, and in general metals, cannot 
be used at high temperatures. Iron reacts with carbon dioxide 
quite rapidly at 400° F., producing carbon monoxide and oxide 
of iron. It also reacts readily with oxygen. An oxidized pipe 
will react with hydrogen causing that gas to disappear as water 
at equally low temperatures. Pipes with rough surface will 
induce a rapid catalytic decomposition of such gases as ammonia 
and some of the less stable hydrocarbons at a rather low red heat. 



SAMPLING AND STORAGE OF GASES 3 

The best materials for sampling tubes are glass, quartz or 
porcelain. These tubes should be protected by a wrapping of 
asbestos in the form of paper or twine and should be slipped into 
an iron jacket which takes the strain off the tube and prevents 
sudden temperature changes. Glass begins to soften about 
600° C. or 1100° F. and on long exposure to a red heat devitrifies 
and ultimately cracks spontaneously on cooling. Porcelain will 
stand about 1000° C. or a little over 1800° F., but at higher 
temperatures the glaze commences to soften. Unglazed porcelain 
will stand a higher temperature and special refractory mixtures 
may be obtained which will not soften at 1700° C. or 3000° F., 
but such tubes are apt to be porous and should only be used if 
proved to be free from leaks. Fused quartz is in some respects 
admirable as a material for sampling tubes, since its coefficient of 
expansion is so small that it never cracks because of temperature 
changes. It will stand 1100° C. or about 2000° F. without 
softening but on long heating tends to become crystalline and 
brittle. The ordinary electroquartz tubes are often porous and 
should be carefully tested. 

4. Types of Sampling Tubes and Their Use. — The simplest 
form of sampling apparatus consists of a single tube through 
whose open end the gases are aspirated. When sampling from 
a large flue the sampling tube is sometimes closed at the end and 
perforated at various points along its length with the expectation 
that gas will be drawn uniformly through the holes at intervals 
across the flue. A device of this sort usually fails of its purpose 
and is often less efficient than a single tube. If the perforations 
are all of the same diameter they will allow the same amount of 
gas to pass through only in case the suction is the same on 
each. This condition can be attained in practice only by 
making the perforations small and the suction high so that it 
will be practically as great at the far as at the near end of the 
sampling tube. But such small holes stop quickly with dust and 
are not practicable. 

A better device to secure a more uniform sample from the gases 
of a flue is shown in Fig. 1. It consists of a bundle of glass tubes 
of the same diameter but of varying lengths which are wired to- 
gether and slipped into an iron pipe not quite so long as the short- 
est glass tube. The glass tubes are cemented into this with neat 



4 GAS AND FUEL ANALYSIS 

Portland cement in such a manner that their ends next the threaded 
joint are all even and about 2 in. from the end of the iron tube. 
This may readily be accomplished in the following manner. 
Plug the threaded end of the iron pipe with a cork and stand it 
vertically on the corked end. Plug one end of each of the glass 
tubes with putty and stand them in the iron tube with their 
lower ends resting on the cork. Fill the iron tube for 3 in. with 
a paste of Portland cement and water and allow to stand for 
twelve hours to harden. The sampler is finished after removing 
the cork and putty by screwing onto the iron pipe a cap which is 
provided with a 1/4-in. nipple to which convenient connection 
may be made. The suction required to draw a slow stream of 
gas through a smooth tube 2 ft. long is only slightly more than 
that required for a 1-ft. tube. The empty space at the end 
of the pipe acts as a mixing chamber and allows a fairly satis- 
factory sample to be drawn through the nipple. 

The sampling tube is to be inserted in the flue in such a way 



Fig. 1. — Multiple gas sampling tube. 

that there will be no leakage around it. An iron gas main may 
be drilled and tapped to receive a threaded nipple into which 
the sampling tube is luted when in use and which is closed by a 
cap when not in use. When a hole must be cut through a brick 
wall a threaded nipple may be cemented permanently into the 
wall and closed, when not in use, with a cap. If only a single 
sampling tube is used it should be inserted to about the point of 
mean velocity of the gases, a subject which is discussed in Chapter 
IX. Where a multiple sampling tube of the above type is used 
it should be inserted so that the longest tube reaches at least to 
the center of the flue. 

It is frequent but bad practice to connect the sampling tube 
and the aspirator by a rubber tube. Rubber is softened and 
burned by hot gases and yields gaseous products which contami- 
nate the sample. It also dissolves tar and hydrocarbon vapors 
and even permanent gases like ethylene in sufficient amount to 
materially change the character of the gas. Furthermore, even 



SAMPLING AND STORAGE OF GASES 5 

the best rubber is never gas tight but always allows some leakage. 
It is usually necessary to use a small amount of rubber tubing 
in making connections, but its use should be restricted to lengths 
of only an inch or two where it serves as a connector between glass 
tubes. When thus used a copper wire should be twisted tightly 
around the rubber where it slips over the glass tube to ensure a 
tight joint. 

5. Aspirators. — The commonest form of aspirator consists 
of a bottle or tank initially filled with water which flows slowly 
out and is replaced by the gas. With this form of aspirator the 
suction constantly decreases as the head of water drops and there- 
fore the flow of gas slackens, which is a disadvantage. This 
may be overcome by making the gas as it enters pass down 
through a central tube and then bubble up through the water on 
the principle of the Marriotte bottle, but unless the water of the 
aspirator has been previously thoroughly saturated with the gas 
this process is certain to change the composition of the gas very 
materially. The extent of the error introduced by failure to 
observe this precaution is discussed later. A film of heavy par- 
affine oil is sometimes poured on the water of the aspirator 
bottle to prevent interaction between the water and the gas. 
Such an oil-film does not, however, prevent the interaction and 
does not even make it much slower. If oil is used it should be at 
least as heavy as a lubricating oil so that it will not give off any 
appreciable volume of vapors which even in small amount will 
cause difficulty in the estimation of oxygen by phosphorus. 
Oil should not be used when the gases sampled contain hydro- 
carbons, since these are quite soluble in heavy mineral oils. 

Where frequent samples are to be drawn a pair of aspirator 
tanks as shown in Fig. 2 are to be recommended. Tanks to hold 
approximately a cubic foot should have the cylindrical portion 
12 in. in diameter and 12 in. high with the cones each 6 in. high. 
They may be made of galvanized iron and will be strong enough 
with merely soldered seams if they are not knocked about too 
much. The ends of the cones terminate in short 1/2-in. nipples 
soldered in. The lower end of the tank carries screwed to this 
nipple a 1/2-in. cock F, and beyond this another 1/2-in. nipple 
with a hose union. The upper nipple carries a 1/2-in. tee on 
whose side-arm is an ordinary 1/4-in. gas cock E, and on whose 



6 



GAS AND FUEL ANALYSIS 



upper end is a cap tapped for a 1/4-in. pipe. This pipe, cut the 
length of the tank, is threaded into the cap from the inside be- 
fore the latter is in place so that when screwed together the 1/4-in. 
pipe runs the whole length of the tank and projects through the 
cap enough to receive the gas cock D. With a pair of bottles 
of this sort the water flows from one to the other and is not 
exposed to the air so that it remains saturated with the gas. 

If a water or steam line is at hand an inj ector may be employed 
as an aspirator. It is desirable in most cases to have the suction 
a slight and steady one, a condition not readily attained with 
injectors running only to a small per cent, of their capacity. It is 
well to have the injector open more widely than is necessary to 
furnish the suction required and to have on the line an automatic 
water seal relief valve as indicated at E in Fig. 3 which will suck 
in air at the inlet of the aspirator if the suction rises too high. 

6. Solubility of Gases in Water. — The solubility of gases in 
water varies with the temperature and the pressure. For our 
treatment it will be sufficient to assume that the gas is always 
under atmospheric pressure and at ordinary room temperatures. 
Under these circumstances the solubility of the common gases is 
as follows: 

SOLUBILITY OF GASES IN WATER 

Expressed as the volume gas dissolved by unit volume water at the tem- 
perature of the experiment when in contact with the pure gas at atmos- 
pheric pressure. 



59° F. 



77° F. 



Carbon dioxide. . . 

Oxygen 

Nitrogen 

Carbon monoxide. 

Methane 

Ethylene 



1.070 


0.826 


0.036 


0.031 


0.019 


0.016 


0.027 


0.023 


0.039 


0.033 


0.147 


0.119 



When mixed gases are in contact with water the amount of 
each gas dissolved will be in direct proportion to its volume and 
its solubility. Thus the composition of pure water saturated 
with air at 59° F. would be 



SAMPLING AND STORAGE OF GASES 



Composition of 
air, per cent. 



Volumes of gases in 100 vols, 
water 



Percentage com- 
position of gas 
dissolved by water 



C0 2 0.04 

2 21.0 

N, 79.0 



0.04X1.07 =0.043 vols. C0 2 
21.0 X0.036 =0.756 vols. 2 
79.0 X0. 019 = 1.500 vols. N 2 



Total dissolved gas =2.299 vols. 



1.9 
32.9 
65.2 

100.0 



The composition of the gases in water saturated with chimney 
gases may be calculated in the same manner. 



Composition of 
gas, per cent. 


Volumes of gases in 100 vols, 
water 


Percentage com- 
position of gas 
dissolved by water 


C0 2 10 

2 10 

N 2 80 


10X1.07 =10.70 
10X0.036= 0.36 
80X0.019= 1.52 


85.0 

2.9 

12.1 




12.58 


100.0 



The change in the carbon dioxide from 10 per cent, of the gas 
sampled to 85 per cent, of the gases dissolved in water shows how 
serious are the errors which can arise in sampling. If the sam- 
pling tank originally filled with pure water should be only half 
emptied so that it would be half filled with gas of the above 
composition and half filled with water, and then it should be 
allowed to stand till equilibrium were attained, 7 per cent, of the 
gas would be dissolved by the water with the following result. 



Composition gas after 

standing over water, 

per cent. 



Original composition 
of gas, per cent. 



Composition of 

gases dissolved by 

water, per cent. 



C0 2 10.0 

2 10.0J 

N 2 80.0 



5.2 
10.4 
84.4 



73.4 

5.0 

21.6 



The above illustration shows that in chimney gases it is not 
at all impossible to have an error of 50 per cent, in the CO2 
through carelessness in sampling. Errors of similar nature, al- 
though hardly of such large proportions, will arise with other gases. 
With illuminating gas it is the important class of illuminants of 



8 GAS AND FUEL ANALYSIS 

the ethylene series which is most seriously affected. If it is 
worth while taking a sample at all it is worth while to saturate 
the water with which the gas is to come in contact. 

7. Saturating Water in Sampling Tanks. — When the gas to be 
sampled is under pressure it may be bubbled through the water 
contained in a bottle, best only about two-thirds full of water 
and loosely stoppered. The air of the bottle will soon be replaced 
by the gas which will thus act on the constantly changing surface 
of the liquid as well as on the surface exposed to the bubbles. 
An occasional vigorous shake will greatly accelerate absorption. 
Under these conditions the water will become practically saturated 
in fifteen minutes. It is not wise to attempt to saturate water 
by bubbling the gas through it while in an open beaker, since the 
constant presence of the air above the liquid defeats the very 
object aimed at. 

The water in tanks of the form shown in Fig. 2 may be readily 
saturated if suction is available by connecting tank 1 to the gas 
main as shown and connecting the suction pipe to cock E. The 
gases will then bubble through the water and pass out E. Where 
suction is not available the procedure is as follows. Start with 
tank 1 full of water and tank 2 empty. Fill tank 1 with gas and 
connect the cocks E on the two tanks with rubber tubing. Raise 
tank 2.. Water will flow from 2 into 1 and gas from 1 to 2. 
When each is approximately half-full close the valves and shake. 
Finish passing the water from 2 into 1 and disconnect the rubber 
tube from E of tank 2. Draw a fresh tankful of gas into 1, 
allowing that in 2 to escape into the air. Connect the cocks E 
with rubber tubes as before and repeat the process of dividing 
the gas and water between the two tanks and shaking. After 
three such operations the water will be sufficiently saturated. 

8. Collecting an Average Sample Representative of a Definite 
Period. — It is frequently desirable to determine the average 
composition of gases flowing through a flue for a period of time 
which may be 15 minutes or 24 hours. If the period is not 
longer than an hour the use of two cu. ft. tanks as shown in Fig. 2 
is satisfactory. A represents the multiple sampling tube pro- 
jecting into a flue. B is a calcium chloride tube loosely packed 
with cotton or asbestos to filter out dust. C is a bubbling tube 
to indicate the rate of flow of the gas. The first step in a test is 



SAMPLING AND STORAGE OF GASES 



9 



to saturate the water of the tanks as previously directed. At 
the close of this operation tank 1 should be full of water and tank 
2 of gas and the sampling tube and the filter should be full of gas. 
To commence the sampling operation D is opened fully and F is 
opened slightly until gas bubbles through C at the rate desired. 
It is a mistake to open widely the lower stopcock on the sampling 
tank and control the flow of gas by partially closing the upper 
stopcock, since with this procedure the gas in the tank is under 




Fig. 2. — Apparatus for aspirating a sample of gas from a flue. 

an unnecessarily reduced pressure and there is an unnecessary 
risk of leakage. The gas in tank 2 escapes through the open 
cock at the top. The pressure gage at G will indicate if the 
sampling tube or the filter becomes choked. The rate of gas flow 
should be so adjusted that tank 1 will be almost filled with gas 
at the end of the period. There should still remain enough 
water to act as a stirrer for the gas when the tank is shaken 
vigorously to mix the contents. This mixing is a simple precau- 
tion which should never be omitted. It is true that gases do 



10 



GAS AND FUEL ANALYSIS 



mix by diffusion but the rate is a slow one and it is never safe to 
rely on diffusion to give a fair sample. After the gas in tank 1 
is mixed a portion may be transferred through cock E to a labora- 
tory gas holder for analysis. To get ready for the next sample 
the E cocks on both tanks should again be connected by the 
rubber tube and the gas transferred to tank 2 so that the water 
in tank 2 will remain saturated. 

If the sampling period is to extend for much more than an 
hour the flow of gas through the sampling tube becomes so slow 
that a multiple sampling tube is not to be relied on. The use 
of the additional apparatus shown in Fig. 3 remedies the difficulty 
where a continuous aspirator is available to draw a rapid stream 
of gas through the sampling tube. The gas filter, bubbling 
tube and sampling tanks of Fig. 2 are to be attached to cock A 
of Fig. 3. The sampling tanks may then be set to take as slowly 



From Samp ling Tubi 




Fig. 3. — Continuous gas sampling apparatus. 



as may be desired a portion of the representative rapidly flowing 
gas stream. 

In Fig. 3, B is a pressure gage to indicate any obstruction of 
the sampling tubes, C is a bubbling bottle to give a visual control 
of the rate of the stream, D is a gas meter which may be omitted 
if not needed, E is a pressure control and F a pressure gage on 
the line from the aspirator. The suction on the sampling tube 
as shown by gage B should be only a few tenths of an inch of 
water. It is difficult, however, to get an aspirator to work prop- 
erly when nearly shut off so that the aspirator is opened enough 
to work efficiently and the suction on the line is kept down by the 
regulator E. The suction on B may be regulated by the depth 
to which the tube in E is immersed. 

The title of this section calls for the collection of a sample 
representative of a definite period. The foregoing procedure 



SAMPLING AND STORAGE OF GASES 11 

only accomplishes it approximately. In order that the sample 
should be truly representative a given proportion, say one-tenth 
of 1 per cent, of the gas, should be constantly passing through the 
sampling tube. If the flow of gas in the main dropped to one- 
third of its former rate, the flow of gas through the sampling 
tube and into the sampling tank should also decrease. The 
ideal to be striven for is to have in the small sampling tank gas 
of the identical composition that there would be in a large gas holder 
where all of the main gas stream had been gathered and mixed. 
This can only be accomplished by a sampler which takes repre- 
sentative quantities as well as qualities of gas. The sampling 
apparatus described is supposed to work at a constant and not a 
proportionate rate, but it does not even do this accurately. 
It is not, however, possible to take a truly proportional sample 
without great elaboration of equipment and the method described 
is usually sufficient. 

9. Collecting a Representative Instantaneous Sample. — The 
problem of a representative instantaneous sample is in some ways 
simpler than that involved in collecting a sample to represent a 
longer period. If the apparatus shown in Fig. 3 is attached to a 
multiple sampling tube a sample drawn at A should be fairly 
representative. If desired an Orsat burette or similar apparatus 
may be attached permanently at A. 

10. Storing Gas Samples. — Samples of gas obtained as directed 
in the preceding section are too large for ready transportation 
to the laboratory for analysis. It is usually convenient to trans- 
fer a portion to a small glass gas holder which is advantageously 
of the type proposed many years ago by Hempel and shown in 
Fig. 4. This consists of a bulb terminated above by the gas 
inlet of capillary tubing bent in the form of a U to allow a water 
seal and at the bottom by a larger tube for the water supply. 
The transfer of gas is accomplished in the following stages. 
Attach at cock E of Figs. 2 and 4 a glass tee carrying at A a 
rubber connection and a small funnel and at B a rubber con- 
nection. Fill the gas holder with water taken from the large 
sampling tank 2 of Fig. 2, which is saturated with the gas, and 
connect the gas holder at B as shown in Fig. 4, with the exception 
of the screw clamps at A and B. Open valve E and blow gas 
through the tee and out A to expel air. Close E and force water 



12 



GAS AND FUEL ANALYSIS 



from the small gas holder into the funnel. Tighten clamp A. 
Fill the glass gas holder nearly full of gas and close E. Open A 
cautiously and allow water to flow from the funnel and fill the 
capillary seal of the gas holder. Close clamp B and disconnect 
the gas holder from the tee. Elevate the levelling bottle so as 
to put the gas in the holder under slight pressure, and close the 
clamp C at the bottom of the holder. The gas is now stored in a 




Fig. 4. — Glass gas holder for storing samples. 

glass vessel closed at the top by a capillary tube filled with water, 
which in turn is closed by a clamped rubber tube at the top of 
the capillary. At the bottom the holder is similarly closed by a 
column of water. The gas is thus in contact with nothing but 
glass and water and if the latter has been previously saturated, 
may be preserved without change for months. The above form 
of gas holder is always reliable. 



SAMPLING AND STORAGE OF GASES 13 

Gas holders of the floating type are not to be relied upon for 
there is always diffusion of gases through the water, and after 
several hours evident changes may be found. There are nu- 
merous forms of gas holders where stopcocks are relied upon to 
prevent leakage. Stopcocks may be tight or they may not and 
anyone who has had experience with the irritating doubts attend- 
ant upon their use will prefer not to trust them more than is 
necessary. The same thing holds true of rubber stoppers and 
connections. Gases may, however, be transported quite safely 
in glass bottles with rubber stoppers provided a little water is 
left in the bottle and the stopper is wired tightly in and covered 
thickly with parafnne. The bottle is then to be kept upside down. 
Under these conditions the small amount of water in the bottle 
forms a seal on the inside and the parafnne a seal on the outside, 
re-enforcing the rubber. When samples of this sort are to be 
shipped by express they should be packed in crates without a top 
so that care will always be taken to keep the proper end up. 
Where gases have to be stored a long time and especially where 
they must be shipped, the truly safe way is to collect them in 
glass tubes drawn out at each end and fuse the ends in a blowpipe 
flame. 



CHAPTER II 
GENERAL METHODS OF TECHNICAL GAS ANALYSIS 

1. Introduction. — Gas analysis is an extremely useful method 
for controlling the operation and checking the efficiency of many 
industrial operations. All of the manifold industries using fuel 
as a source of heat and almost all industries engaged in producing 
fuel or utilizing it in any way find in gas analysis a valuable 
assistant. There are very many special industries which require 
the analysis of gases which are peculiar to themselves and not 
connected with fuels., but though the general methods of gas 
analysis here given will often apply to these cases, no attempt 
will be made to develop those applications which might better 
be taken up in connection with a study of the particular indus- 
tries. This chapter will consider only the gases arising from the 
utilization of fuels. 

The purpose for which the analysis is desired will influence 
the methods to be employed and the kind of apparatus to be 
used, for time consumed and liability to errors increase rapidly 
with the number of constituents to be determined. The analysis 
is to be made as simply as possible, small percentages of gases 
unimportant for the purpose of the analysis being neglected and 
groups of related gases being frequently determined together. 
In boiler firing and in the operation of all furnaces heated by 
combustion of fuel, the variations in the percentages of carbon 
dioxide, oxygen and carbon monoxide show at once the changes 
in efficiency of the furnace. In the operation of gas producers 
these three constituents with the added determination of hydro- 
carbons and of hydrogen suffice for most purposes. When gas 
is to be sold to consumers, as is the case with a city gas supply, 
a more complete analysis is often necessary and not infrequently 
some uncommon and minute constituents must be sought as an 
explanation of trouble. 

This adaptation of the means to the end is a characteristic of 
technical analysis, which seeks only the particular information 

14 



GENERAL METHODS OF TECHNICAL GAS ANALYSIS 15 

of value for the purpose in hand. On this account gases from 
different sources will be considered separately, although there 
may be much in common between them. There are various 
operations common to almost all processes of gas analysis which 
may well be considered before passing to special cases, and 
such general considerations form the subject of this chapter. 

2. General Method. — The method preferably followed in 
technical gas analysis requires a measurement of the initial 
volume of the mixed gas, the absorption of a single constituent 
by an appropriate reagent, and the measurement of the new 
volume, the constituent absorbed being determined by difference. 
Where no suitable absorbent is known for a given constituent 
it is desirable to transform the gas into some more suitable 
compound. It is necessary in order that these changes in volume 
due to absorption be correctly noted, that the temperature and 
pressure of the gas be known at each step, and it would be ideal 
if both the temperatures and pressures could be kept absolutely 
constant throughout the process. This can never be accom- 
plished, although by special apparatus described in Chapter VI 
on Exact Gas Analysis errors due to change in external tem- 
perature and pressure during an analysis may be automatically 
eliminated. This procedure is, however, more complicated 
than is necessary for technical work where it is usually suf- 
ficiently accurate to make the assumption that the temperature 
of a water-j acketed burette in a laboratory does not vary during 
the hour that may be required for an analysis, and that the 
barometric pressure does not change in the same period. Since 
this simpler procedure is sufficiently accurate for most technical 
purposes, it will be described first. The historical development 
of the present apparatus and methods is discussed in Chapter VI 
on Exact Gas Analysis. 

3. The Gas Burette. — The gas burette has its zero point 
at the top and is usually of 100 c.c. capacity. It is closed at the 
top by a stopcock or sometimes simply by a rubber tube and a 
pinchcock and should always be enclosed in a. water jacket. 
Almost all forms of gas burettes will answer the -above descrip- 
tion, but there are many differences of detail, the most impor- 
tant being the style of the stopcock which closes the burette at 
the top. The form of apparatus which has been evolved in 



16 



GAS AND FUEL ANALYSIS 



the laboratory of the University of Michigan 1 and which has, 
given good service during the past ten years is shown in Fig. 5, 
which illustrates the apparatus as it appears in service. 
Details are given in Fig. 6. The burette-stand may be im- 
provised from an ordinary iron stand, one of whose rings of ex- 
ternal diameter slightly greater than the water jacket of the 
burette has been provided with a brass collar, thus making a 





Rubber Stopper 




C. 



JL 



TT 



100 c.c. divided D - 

into± c.c. im 

H Rubber Stopper Q ' ~V 



Fig. 5. — Gas burette and 
pipette. 



IT 



Fig. 6. — Details of gas burette. 



cup in which the rubber stopper of the water jacket rests without 
binding. Another ring large enough to slip loosely over the 
water jacket serves to keep the burette vertical. A segment 
is sawed out of the front of this ring to allow an uninterrupted 
view of the graduations, and it is wrapped with chamois skin 
until it fits as snugly as desired. A spring clamp made from 
sheet brass makes a more elegant upper support. By this simple 
arrangement the burette may be raised, lowered, or swung to 

1 White and Campbell, J. Am. Chem. Soc, 27, 734 (1905). 



GENERAL METHODS OF TECHNICAL GAS ANALYSIS 17 

one side at the convenience of the operator, and may be tipped 
in any position while carrying, without danger of breakage. 

By reference to A of Fig. 6 it will be seen that the body of 
the burette is a perfectly straight tube. It is closed at the bottom 
by a one-hole rubber stopper, which need not even be wired in, 
unless the burette is to be filled with mercury. To clean the 
burette, all that is necessary is to take out the rubber stopper 
and lift the burette and its jacket out of the rings when it may 
be turned upside down, swabbed out as an ordinary burette, 
and then swabbed with a clean dry muslin which is more efficient 
than a wet cloth in removing the film- of grease which causes 
the drops to hang to the glass. Caustic soda may be used or 
chromic acid, but they are not usually necessary. 

4. Care of Stopcock. — The stopcock of a gas burette is very 
carefully ground and polished so as to be as nearly gas tight as 
possible. Particles of grit getting into the capillary opening 
are apt to cut a groove around the stopcock so the opening is 
bored diagonally in order that the grooves worn in this manner 
may be parallel and non-connecting. This device is of assistance 
but the stopcock must still be handled carefully. 

To keep in good condition remove the stopcock from the 
burette, wipe it off with a dry cloth and see that the capillary 
openings are clean. Do the same with the seat into which it 
fits in the burette and the capillaries with which it connects. 
Rub a thin coat of some lubricant over the stopcock. Vaseline 
is inferior. A material made by melting one part of best black 
rubber at as low a temperature as possible and stirring into it 
one part of paraffine and one part of vaseline answers well when 
it is carefully made. The author has found anhydrous lanolin 
the best material. The lubricated stopcock should be pressed 
gently into the dried seat and turned a couple of times, when 
the space between the stopcock and the seat should appear 
perfectly translucent without air bubbles or any discontinuity. 
If too much lubricant is used it will work itself into the capillaries 
and clog them. If either the stopcock or the seat is wet the 
lubricant will not adhere well. These stopcocks are expensive 
and it is advisable to fasten them to the burette with a fine 
copper wire attached to the stopcock so loosely that it can 
turn readily. It is not advisable to use a rubber band for this 



18 GAS AND FUEL ANALYSIS 

purpose since it sticks to the handle of the stopcock and exerts 
a torsion sufficient sometimes to turn the cock at an inopportune 
time. The stopcock should always be loosened in its seat when 
the burette is to be put away and it is admirable policy to 
always clean it and make it ready for use again before setting it 
aside. 

5. Saturating the Water of the Burette. — The liquid filling 
the burette is almost always water which allows much more 
rapid and convenient and in some ways more accurate manipula- 
tion than mercury does. It should be saturated with gas 
similar to that which is to be analyzed. If the gas is air this 
precaution may often be omitted, since distilled water is usually 
saturated with air. The precaution should not be omitted with 
other gases, especially those like flue gases rich in the more 
soluble carbon dioxide. The errors due to solubility of gases 
are discussed more fully in Section 6 of Chapter I. Place 200 
c.c. of water in a flask or bottle of about 400 c.c. capacity and 
lead in a stream of gas through a glass tube passing through a 
loosely fitting cork, shaking occasionally. If the supply of gas 
is limited a smaller flask may be used and the loose cork may 
be pressed down tight after the air has been displaced. Shaking 
the flask facilitates absorption. It is not necessary that the 
water, be absolutely saturated and five minutes is usually ample 
time for the operation. 

6. Drawing the Sample of Gas into the Burette. — The gas 
to be analyzed is assumed to be contained in a gas holder of a 
type similar to that shown in Fig. 4 of Chapter I, but the 
directions for use of this type of gas holder may readily be 
adapted to other types. 

The tubing to connect the burette and gas holder should be 
capillary so that the air contained in it may be completely 
swept out without wasting much gas. A tube of 1 mm. internal 
diameter answers well. It should not be rubber because rubber 
absorbs heavy hydrocarbons from gases rich in these bodies 
and gives them back again to gases containing them in but 
small amount. It is necessary to make one rubber connection 
at each end of the capillary tube but the surface of rubber 
exposed to the action of the gases should be reduced to a minimum 
by bringing the ends of the glass capillary tubes into direct 



GENERAL METHODS OF TECHNICAL GAS ANALYSIS 19 

contact with each other, or, if it is necessary to leave a pinch- 
cock on the rubber, as close to each other as possible. The 
glass tubes should be cut off square and the sharp edges softened 
in a flame sufficiently to prevent the cutting of the rubber but 
not enough to constrict the capillary opening of the glass tube. 
The rubber tube should fit tightly to the glass and be of the 
best quality black gum rubber, free from any internal ridge 
where the seam has been joined. The inside of the rubber tube 
may be moistened with water or preferably with glycerine to 
make it slip more readily over the glass. The rubber connec- 
tions to the capillary should be bound with wire as a further 
safeguard against leakage. Soft copper wire of about 22 B. & 
S. gage is suitable. Finer wire is too apt to cut the rubber. 
Heavier wire is apt not to pull up snugly. Copper wire of 24 
B. & S. gage insulated with cotton and paraffined like that 
used for annunciators, is the best material as it is strong enough 
and does not cut the rubber. It is a mistake to wrap the wire 
several times around the tube. A piece of wire about 2 in. 
long should be wrapped once around the tube. The crossed 
ends are then to be grasped close to the rubber with a pair of 
pliers and tightened with a single half turn of the wrist. 

No rubber joint can be relied on to be gas-tight for a long 
period of time. A joint prepared as directed here should, how- 
ever, not allow any perceptible leakage in the course of a gas 
analysis although it is wiser not to subject it to any higher gas 
pressure or suction than necessary. 

The method of connecting the gas holder and the burette 
is shown in Fig. 7 where A is the gas holder, D, a bent capillary 
tee tube and F the gas burette. Before making the connections 
the gas burette is to be filled with saturated water and the cock 
closed by a turn of 180° which completely seals both the capil- 
laries below and above the cock. The capillary tee tube is to 
be inserted into the open rubber tube above the clamp B, con- 
nected at E as shown and the joints are to be wired. The gas 
in the holder is to be put under pressure by raising the levelling 
bottle and clamp B opened. Cock C is then opened slightly 
until the water in the capillary of the gas holder rises to displace 
all the air in the funnel arm. Cock C is then closed and cock F 
turned 90 degrees to the position shown in Fig. 7 and at B in 



20 



GAS AND FUEL ANALYSIS 



Fig. 6. The rest of the water in the capillary A moves through 
D and out F driving all air ahead of it. Some gas may also 
blow out if the manipulator is not skilful, but this does no 
harm. Cock F is then turned 90 degrees opening the passage 
to the burette as shown at A in Fig. 6 and the gas passes into 
the burette. When enough gas is in the burette another 90- 




Fig. 7. — Gas burette and gas holder. 

degree turn of the cock in the same direction to the position C 
of Fig. 6 stops the gas flow. A few cubic centimeters of water 
are placed in the funnel above C (Fig. 7), the pressure in the 
gas holder is changed to suction, cock C is opened and water 
flows into the capillar of the gas holder re-establishing the 
seal. The clamp B may then be closed and the capillary 
disconnected. This procedure allows transfer of the gas without 



GENERAL METHODS OF TECHNICAL GAS ANALYSIS 21 

possibility of change in composition and restores the seal of 
the gas holder at the close of the operation. Instead of the 
tee with cock and funnel blown as one piece the simpler apparatus 
shown in Fig. 4 of Chapter I may be used. 

7. Measuring a Gas Volume. — The volume of gas is to be 
measured at the temperature of the water jacket and at baro- 
metric pressure. The temperature of the gas as drawn into 
the burette does not ordinarily differ very many degrees from 
that of the jacket water but it should be allowed to stand a 
few moments to allow it to attain that temperature. During 
these minutes the gas if not already saturated with moisture 
rapidly absorbs it from the moist burette walls and becomes 
saturated as it should be before its volume is measured. 

Delay in reading the volume is also necessary to allow the 
film of water which adheres to the burette walls as the sample 
is rapidly drawn in, to run down. If the walls of the burette 
are clean the water will have run down in three minutes so 
completely that the volume has become approximately constant. 
If this precaution is neglected the volume read may easily be 
in error by 0.2 c.c., even with a clean burette. Some operators 
object to this three-minutes wait as too great hindrance to rapid 
work and it is true that if the readings are made by a skillful 
operator immediately after the introduction of the gas, the 
errors of successive readings are almost constant and disappear 
in the subtractions. If, however, the practice is followed of 
detaching the used pipette and connecting the new one before 
reading the volume of gas, sufficient time will have elapsed 
without the operator's having been idle. 

To obtain a sample of exactly 100 c.c. a sample of slightly 
more than 100 c.c. is initially taken and compressed by raising 
the levelling bottle until the bottom of the meniscus is exactly 
opposite the 100 c.c. mark. The stopcock at the bottom of 
the burette is then closed so that the mensicus cannot change its 
position and the stopcock at the top of the burette opened momen- 
tarily to the air, to allow the pressure in the burette to equalize 
itself with the outside air. The volume of gas should now be 
100 c.c. at atmospheric pressure but the correctness of the 
volume should be checked by opening the stopcock connecting 
the levelling bottle with the burette and raising the levelling 



22 GAS AND FUEL ANALYSIS 

bottle until its water surface is at the same height as that of the 
water in the burette. The connecting stopcock may now be 
closed and the volume read as indicated by the bottom of the 
meniscus. If the operation has been properly carried out the 
volume should be exactly 100 c.c. This volume is subject to 
correction for error in the burette and if an exact 100 c.c. sample 
is desired the meniscus may have to be set on some other figure 
than the 100 mark. 

8. Calibration of a Gas Burette. — A gas burette may be 
calibrated like any other form of burette by wiring a one-hole 
rubber stopper carrying a stopcock into the bottom of the 
burette and weighing the water delivered. Burettes of good 
quality are usually calibrated accurately enough throughout 
their cylindrical portion to make this form of calibration unneces- 
sary for technical work. The burette should, however, be cali- 
brated in its upper portion, especially if its previous history 
is not definitely known, since its original stopcock may have 
been broken and the volume of the neck changed when a new 
stopcock was fused on, and since it may have been calibrated 
by the maker to be used when filled with mercury instead of 
with water. The error in this latter case arises from the custom 
of reading the mercury meniscus at the top of its convex surface 
and the water meniscus at the bottom of its concave surface. 
It will be readily seen that if the mercury meniscus stands at 
10 c.c. there will be more gas in the burette than if the same 
burette is filled with water with the bottom of its meniscus at 
10 c.c. This error may amount to 0.2 c.c. in an ordinary burette. 
Both of these errors are constant ones throughout the cylindrical 
portion of the burette and independent of the volume of gas in the 
burette. It will therefore be sufficient to determine them once. 

The most convenient method is to compare one burette with 
another. Draw into each burette about 10 c.c. of air, the 
exact amount being entirely immaterial. It is only necessary 
that the volume be large enough so that the reading is in the 
cylindrical portion of the burette. It is not desirable that the 
volume be large since the error caused by water adhering to 
the walls of the burette increases with the size of the sample. 
Connect the burettes by a bent capillary tube making the 
rubber connections while the stopcock of one of the burettes is 



GENERAL METHODS OF TECHNICAL GAS ANALYSIS 23 

open to the air so that the air enclosed in the capillary will be 
under atmospheric pressure. Read the volume of the air in 
each burette at atmospheric pressure as usual. We will assume 
that Burette A which has an unknown constant error "x" is 
the one being tested and that Burette B is the one assumed to 
be correct throughout its cylindrical portion, although it may 
itself have a similar unknown constant error "y." Transfer 
all of the air from A to B stopping the water in A just at the 
stopcock and read the new volume in B. The notes will then 
read somewhat as follows: 

Calibration of Burette A Againt Burette B 



Burette A 
Initial vol. air 10.6 c.c.+x 
Second reading 


B 

9.5 c.c.+y 
20.3 c.c.+y 


Subtracting 10.6 c.c.+x = 
x = 


= 10.8 c.c. 
= +0.2. c.c. 



This result translated into words means that there must be 
added to each reading of Burette A 0.2 c.c. Since the probable 
error of observation is 0.1 c.c. several successive determinations 
should be made and the mean taken. 

It is always wiser to record this error in the notebook after 
each reading, 92.5 + 0.2, and not simply make the correction 
mentally and record 92.7, since there may always come a time 
when, the analyst will be in doubt as to whether he has made 
the mental correction or forgotten to make it before recording. 
This error automatically disappears whenever one volume is 
subtracted from another and it is therefore only necessary to 
apply it when the absolute volume needs to be known as is the 
case with the initial volume taken for analysis. This makes 
the error vastly less important than it would be otherwise, for 
if in an analysis of flue gas an apparent 100 c.c. sample is taken 
which becomes when corrected 100.2 c.c, and 10 c.c. is found 
to be C0 2 , the percentage of C0 2 , neglecting the burette calibra- 
tion, is found to be 10.00 per cent, and allowing for the calibra- 
tion 9.98 per cent., which when rounded off becomes 10.0 per 
cent, as before. The case is different, however, when a sample 
of 10.0 c.c. is taken as is the case in explosion analysis. If the 



24 



GAS AND FUEL ANALYSIS 



analysis showed 8.0 c.c. of hydrogen, the percentage neglecting 
the calibration would be figured as 80.0 per cent, but allowing 
for the calibration would be 78.4 per cent. It is preferable to 
record the calibration correction even though it may be later 
neglected in the calculation. 

9. Gas Pipettes. — The various gases are determined so far 
as possible by absorption in suitable reagents contained in 
pipettes of the form shown in A, B, and C of Fig. 8. The use of a 
separate pipette for each reagent was first brought into general 
use by Hempel. These pipettes differ from his in the elimination 
of the deep U bend in the capillary, which is retained only in the 
explosion pipette. This deep bend is a distinct disadvantage 



c. 






Fig. 8. — Details of gas pipettes. 



since drops of reagent collect in it and are later carried into the 
burette. It is no longer needed when used with the burette 
just described. These pipettes are mounted on wooden stands, 
as shown in Fig. 5, which should be paraffined and not shel- 
lacked so that they may not be affected by reagents accidentally 
spilled. 

10. Connecting the Burette and Pipette. — The greatest 
manipulative error with most forms of gas analysis apparatus 
comes from the frequent changes of pipettes necessary. Unless 
the operator is skilful there is danger of loss of gas or inclusion 
of air. The form of burette just described prevents this error. 
The general arrangement of the burette and pipette is shown in 
Fig. 5. The stopcock A is turned to the position shown at B in 



GENERAL METHODS OF TECHNICAL GAS ANALYSIS 25 

Fig. 6, the bent capillary B whose dimensions are immaterial, 
is connected to the burette and pipette and the rubber joints 
are wired. The operator blows through the rubber tube (D of 
Fig. 5) on the last bulb of the pipette, forces the liquid from the 
pipette up the capillary and over to the stopcock, driving all 
the air ahead of it, and closes the stopcock by turning it 90° 
to the position D of Fig. 6. The capillary tube is now entirely 
full of liquid and the operator has only to compress the gas in 
the burette by raising the levelling bottle, and turn the stopcock a 
half turn to the proper position (A of Fig. 6) when the gas will 
pass into the pipette. By this method of manipulation, it is 
easy to transfer the gas from burette to pipette without loss or 
inclusion of air. Furthermore, since the volume of the capillary 
is entirely immaterial, it may be chosen of larger diameter than 
usual, permitting more rapid work and lowering the pressure 
necessary to force the gas through it rapidly. It has been 
found advantageous to have the stopcock left-handed, as indi- 
cated, so that the hand manipulating the stopcock may not 
interfere with a clear view of the meniscus of the liquid advancing 
along the capillary tube. 

11. Details of a Simple Gas Analysis. — Accuracy in gas 
analysis is dependent on the exercise of very great care in ma- 
nipulation. When the analysis is completed there is no way of 
going back over the ground again as may so frequently be done 
in ordinary chemical analysis, and it is not always possible to 
make duplicate analyses. The analyst must be able to state 
with confidence that every precaution was taken to ensure an 
accurate result. Detailed directions will be given for the 
analysis of a gas which may be assumed to be air. This is a 
very convenient material for practice since it may be obtained 
in unlimited quantities and of practically constant composition. 

The burette is to be cleaned (§ 3), the stopcock lubricated 
(§4), and the water saturated (§5). Draw the sample of gas 
into the gas burette (§6), measure it (§ 7), and connect it to a 
pipette containing KOH (§ 10), for determination of CO2. 
The connections having been properly made and the air driven 
out of the capillary tube as indicated, raise the levelling bottle 
and pass the gas into the absorbent, letting the water of the 
burette follow until it reaches the bottom of the capillary of 



26 GAS AND FUEL ANALYSIS 

the pipette. The gas is now all in the pipette. Let it remain 
for about three minutes gently shaking the pipette occasionally 
to agitate the gases and cause more rapid absorption. When 
it is believed that absorption is complete pass 1 c.c. of the 
burette water into the pipette to rinse from the capillary any 
reagents which might have been splashed into it, and then draw 
back the gas into the burette, pulling the liquid of the pipette 
as far as the stopcock on the burette. By a quarter turn of 
the stopcock to position B of Fig. 6 the connection between the 
pipette and the burette is closed while that from the pipette to 
the air is open. This causes the reagent to siphon back into 
the pipette. After waiting for three minutes to allow the 
liquid to drain from the walls of the burette read the volume 
as before and report the decrease in volume as the volume of the 
C0 2 absorbed. There is no certainty that all the gas has been 
absorbed. The only way for the operator to be sure is to pass 
the gas back again into the pipette and repeat the operation 
until the volume remains constant. Disconnect the pipette 
from the capillary tube, and rinse out the capillary tube with 
the wash bottle shown at E of Fig. 5, thus completing the first 
step of the analysis. If the gas being analyzed is air, the 
volume after treatment with KOH should be the same as before 
since the volume of C0 2 in the air, 0.04 per cent., is too small to 
be measured with a burette of this type. 

In the practice analysis of air the next determination would 
be that for oxygen which would be absorbed by phosphorus 
or alkaline pyrogallate as directed in §§ 3 and 4 of Chapter III. 
Air contains 20. 9 per cent, of oxygen by volume. The residue is 
assumed to be nitrogen. 

Successive analyses of similar gases may be made without 
changing the water in the burette provided that none of the 
reagents have been carelessly drawn into the burette. The 
greatest danger is from the caustic solution which will absorb 
some of the C0 2 from a newly introduced sample before its 
volume has been measured. Phenolphthalein in the water 
will show when it has become alkaline and should be changed. 
There is no objection to having the burette water faintly acid 
and there is the advantage that small amounts of alkali are 
neutralized and rendered harmless. 



GENERAL METHODS OF TECHNICAL GAS ANALYSIS 27 

12. Accuracy of the Analysis. — Account should now be 
taken of the magnitude of various possible errors, some of 
which have not been mentioned. The smallest division on 
the burette is usually 0.2 c.c. and the volume may not with 
certainty be estimated by interpolation closer than 0.1 c.c. 
This probable error limits the accuracy of the process to 0.1 per 
cent, with a sample of 100 c.c. and an accuracy of 1.0 per cent, 
with a sample of 10 c.c. Change of temperature of the burette 
water during an analysis causes a change of 0.36 per cent, in 
the volume of the gas for each degree centigrade. Change of 
barometric pressure causes a change in volume of 0.13 per cent, 
for each millimeter of mercury change in pressure. There are 
other minor sources of error which will be mentioned in Chapter 
VI under " Exact Gas Analysis." It will be evident that it is 
perfectly useless to expect an accuracy of greater than 0.1 per 
cent, with apparatus of this type, and that an error of 0.2 per 
cent, is not improbable. An analyst who reports an analysis 
carried to hundredths of a per cent, only shows his own ignorance. 



CHAPTER III 

ABSORPTION METHODS FOR CARBON DIOXIDE, UN- 
SATURATED HYDROCARBONS, OXYGEN, CARBON 
MONOXIDE AND HYDROGEN 

1. Carbon Dioxide. — This gas is determined by absorption 
in a strong solution of either caustic soda or potash. Very 
concentrated solutions dry the gas and make it necessary to 
let it stand in the burette before reading the volume until it 
has again become saturated with moisture. Dilute solutions 
work too slowly. A solution of 50 grm. NaOH in 150 c.c. of 
water is recommended to be kept in the form of pipette shown 
in A of Fig. 8. The absorption is rapid, three minutes being 
always ample. The reaction may be accelerated by gently 
shaking the pipette or by passing the gas back and forth. Glass 
rods or perferably glass tubes are sometimes introduced into 
the pipettes to accelerate the absorption by offering a large 
wetted surface with which the gas may come in contact. If 
this device is used care must be taken that no gas bubbles are 
trapped in the pieces of glass tubing as may frequently be the 
case if they are less than 5 mm. internal diameter or if they do 
not stand vertically. If it is desired to place glass tubes in the 
pipette use the form shown in B of Fig. 8. It will be necessary 
to wire the rubber stopper firmly into place to prevent leakage 
of the caustic. 

This reagent absorbs not only carbon dioxide but also sulphur 
dioxide, hydrogen sulphide and any other acid vapors which 
may be present. It may be used until almost all of the caustic 
has been changed to carbonate. One pipette will absorb about 
four liters of C0 2 . There will be slow carbonate formation 
through exposure to the air but the reagent may be used with- 
out fear for several months provided it is used infrequently. 

2. Unsaturated Hydrocarbons. — These gases are determined 
by absorption in a liquid which by addition forms saturated 
compounds from the unsaturated ones. In gases from coal the 

28 



ABSORPTION METHODS 29 

predominating constituent is ethylene, C 2 H 4 , but smaller per- 
centages of the other olefines are present and sometimes small 
amounts of acetylene, C 2 H 2 . A solution of bromine water 
made by diluting one volume of saturated bromine water with two 
volumes of water is the reagent preferred by the author. It is 
placed in the first bulb of the double pipette shown in C of 
Fig. 8, and the third bulb is filled with water to lessen the diffu- 
sion of bromine into the air of the laboratory. If the solution 
becomes bleached through formation of hydrobromic acid in the 
sunlight, it is sufficient to add a few drops of liquid bromine which 
again brings it up to its normal strength. It is unnecessary to 
have it so strong that the gas drawn back into the pipette shows 
pronounced yellow bromine fumes. When gases with more 
than a small per cent, of unsaturated hydrocarbons are brought 
into contact with bromine it is possible to observe the formation 
of the bromide as an oily film on the surface of the liquid. As 
this film retards reaction between the bromine and the gas, it is 
advisable to shake the pipette gently during absorption, when 
little drops of the heavier ethylene bromide may be seen falling 
to the bottom of the pipette. The gas drawn back into the 
burette will contain so much bromine vapor that its volume 
may even have increased in the process. It must be passed into 
a caustic solution and shaken for about one minute to remove 
the bromine fumes and then brought back into the burette and 
measured. The diminution in volume is to be reported as 
unsaturated hydrocarbons. A delicate test for the complete 
removal of these constituents is afforded when phosphorus is 
subsequently used as a reagent for oxygen. A fraction of a 
tenth of a per cent, of ethylene will completely prevent the 
reaction between phosphorus and oxygen. Three minutes 
shaking with the bromine is sufficient to remove the unsaturated 
hydrocarbons from most gases, but gases of high candle power, 
like Pintsch gas, sometimes require ten minutes. Treatment 
with bromine water should be repeated until phosphorus smokes 
when the gas is brought in contact with it. 

Fuming sulphuric acid acts in the same way as does bromine 
water, but it is difficult to handle, attacks rubber tubing badly, 
and must be protected from the moisture of the air to avoid loss 
of efficiency. 



30 GAS AND FUEL ANALYSIS 

3. Oxygen by Phosphorus. — Yellow phosphorus is an extremely 
reliable reagent for the absorption of oxygen when used under 
proper conditions. It combines with oxygen producing solid 
oxides of phosphorus and reacts with almost no other gases 
which might be present. The disadvantage attending its use 
is the danger of the reaction not taking place at all because 
of the presence of inhibiting catalyzers, because of too low tem- 
perature or because of too high a concentration of oxygen 
in the gas. There is, however, easy ocular evidence of the 
reaction so that there need be no uncertainty as to whether 
the reaction has taken place. When once started it goes to 
completion. 

The pipette is of the form shown in B of Fig. 8. To prepare 
it for use the pipette is inverted and filled with water and into 
it are dropped sticks of phosphorus about 5 mm. in diameter 
which have been cut to proper length under water. The sticks 
are to stand vertically and fill the pipette practically full. The 
only advantage of the small sticks lies in their greater surface 
and in the convenience with w r hich the pipette may be filled. It 
is possible to prepare them in the laboratory by melting phos- 
phorus under water at a temperature a little above 44° C. and 
sucking it into a slightly conical glass tube. With expert 
manipulation this tube may be lifted from the w r arm water and 
plunged into cold water where the phosphorus will soldify and 
contract so that the stick may be pushed from the tube. It is 
simpler though not so elegant to mould the sticks in a tin dish 
about 5 in. long made with a corrugated bottom and provided 
with a rim about an inch high and a handle. This mould 
is submerged in a dish of warm water and enough phosphorus 
melted in it to fill the corrugations. It is then lifted out and 
placed in cold water till the sticks become solid. Molten phos- 
phorus catches fire instantly in the air and produces dangerous 
burns on the skin. Particles of solid phosphorus dropped in 
cracks of a wet table or floor have been known to smoulder 
twenty-four hours and finally burst into flame. Great care 
must always be exercised in handling phosphorus and it is 
usually preferable to buy it already cast in small sticks. The 
pipette should be kept in the dark when not in use to avoid the 
deterioration of the phosphorus. Pipettes made from brown glass 



ABSORPTION METHODS 31 

retard the action of the sunlight. With proper care a phos- 
phorus pipette should last for years without refilling. 

When a gas containing oxygen is introduced into a phosphorus 
pipette there normally appears at once a dense white cloud of 
oxides of phosphorus which are evident even when the amount 
of oxygen is less than 0.1 per cent, of the total volume. All tech- 
nical gases will contain this much oxygen, for even if they did 
not contain it originally they will have absorbed it from the water 
of the sampling apparatus or of the burette, so that the presence 
of these clouds is a sure indication that the reaction is progressing 
properly. Conversely the absence of any smoke means not that 
there is no oxygen present, but that there is something preventing 
the reaction. The reaction between oxygen and phosphorus 
is also attended by a glow, visible only in the dark, which disap- 
pears with the completion of the reaction. The white cloud con- 
sists of solid particles of phosphoric oxides which slowly settle and 
dissolve in the water. It is not necessary to wait for this, how- 
ever, before drawing the gas back into the burette and measuring 
the oxygen absorbed for the particles possess very slight vapor 
tension and do not occupy an appreciable volume. The reaction 
should with certainty be completed in three minutes if the white 
smoke appears promptly and if the surface of phosphorus exposed 
is large. It will not accelerate the reaction to shake the pipette 
since the reagent is a solid and the pipette is so closely filled 
with sticks that diffusion will soon bring the oxygen to the sur- 
face of the phosphorus. 

The sticks of phosphorus at first yellow and waxy become 
covered with a reddish crust on long exposure to light and are in- 
active. Such sticks may be melted under water, skimmed, and 
cast into new sticks. The inactive crust may also be removed 
by placing in the pipette a 10 per cent, solution of K 2 Cr 2 07 
made faintly acid with H 2 S0 4 . The chromate becomes reduced 
to the green chromic salt with oxidation of the surface of the 
phosphorus. It is preferable, however, to avoid deterioration 
by keeping the pipette in the dark when it is not in use. 

If the white vapors do not appear promptly when the gas is 
passed into the pipette, the explanation may be sought in four 
directions. 

a. The temperature may be too low. It should be above 15° C. 



32 GAS AND FUEL ANALYSIS 

b. The concentration of the oxygen may be too high. Moist 
phosphorus does not react at all with perfectly pure oxygen at 
ordinary room temperature. If the partial pressure of the oxygen 
is diminished either mechanically by an air pump or by dilution 
with an inert gas the reaction commences. With 50 per cent, 
oxygen it is violent, flame being produced and the phosphorus 
melting. There is danger of breaking the pipette. When the 
concentration is less than 30 per cent, the reaction proceeds 
quietly and the phosphorus does not melt. 

c. An inhibiting catalyzer may be present. The most com- 
monly occurring catalyzer is ethylene, a few hundredths of a per 
cent, of which completely prevents the reaction between phos- 
phorus and oxygen. Acetylene, benzine, ether, hydrogen sul- 
phide and many other substances possess similar though usually 
weaker powers. Fortunately they are practically all removed 
either mechanically or chemically by bromine water followed by 
caustic potash and the gas should always be thus treated if the 
white fumes fail to appear promptly. 

d. The phosphorus may have been rendered inactive by a 
heavy dose of a catalyzer. It may be restored by replacing the 
water in the pipette with fresh water and passing several successive 
samples of air into the pipette until the phosphorus again smokes 
freely. 

Commercial compressed oxygen should be diluted with nitro- 
gen before analysis. The nitrogen may be conveniently pre- 
pared from air by passing a buretteful of air into the phosphorus 
pipette, disconnecting the pipette and closing it with a pinchcock. 
Twenty-five to thirty cubic centimeters of the oxygen are then 
to be drawn into the burette (note that a calibration error of 
0.3 c.c. means 1 per cent, here) and the phosphorus pipette recon- 
nected. There will be sufficient nitrogen in it to flush out the 
capillary connecting tube and fill the burette as well. The 
oxygen may now be absorbed by phosphorus. It is desirable 
to introduce the oxygen into the burette before the nitrogen 
which thus fills the upper part of the burette and comes in contact 
first with the phosphorus. If the reverse procedure were fol- 
lowed and the oxygen introduced in the burette last, it might 
be brought in concentrated form in contact with the phosphorus 



ABSORPTION METHODS 33 

and cause violent combustion, a trouble which the above scheme 
of procedure avoids. 

4. Oxygen by Alkaline Pyrogallate. — This reagent is very 
frequently used, especially in apparatus of the Bunte or Orsat 
type. When used with proper precautions it gives accurate 
results. Pyrogallol is a trihydric phenol C 6 H 3 (OH) 3 which in 
alkaline solution is a strong reducing agent, becoming itself 
oxidized to other products. Unfortunately, unless the solution 
is freshly prepared and strongly alkaline there is danger of carbon 
monoxide being evolved as oxygen is absorbed. This not only 
causes the oxygen to be reported low, but also makes the carbon 
monoxide high. Berthelot has shown that a reagent made by 
taking a solution of 1 part of pyrogallol in three of water and 
mixing it with its own volume of a solution of 1 part of KOH in 
two of water will, when freshly prepared, absorb ten times its 
volume of oxygen without giving back more than a trace of CO, 
but that solutions which have been used too long or do not con- 
tain enough alkali may give up as much as 5 per cent, of the 
volume of oxygen absorbed as carbon monoxide. 

The reagent should be kept in a double pipette (C of Fig. 8), 
the third bulb being filled with water to prevent action of the 
air on the reagent. It may also be kept in a single pipette 
(A of Fig. 8) provided a rubber balloon is fastened to the second 
bulb for the same purpose. The reagent works very slowly at 
temperatures below 15° C. Carbon dioxide and other gases 
which would be absorbed by alkali must be removed before 
testing for oxygen with pyrogallate. 

Mr. H. A. Small in the author's laboratory tested the behavior 
of a solution of pyrogallate made up according to Berthelot's 
directions and kept in an ordinary four bulb pipette without 
any special precautions to prevent diffusion of oxygen into the 
pipette. Duplicate samples of air were analyzed almost 
daily for more than a month. During the first four weeks the 
reagent absorbed the proper percentage of oxygen although 
it was frequently necessary to shake more than three minutes 
to accomplish this. The 150 c.c. of reagent in the pipette had 
up to this time absorbed 1140 c.c. of oxygen. After this the 
absorption of oxygen became incomplete, the line of demarca- 
tion being quite sharp and the apparent oxygen of the air drop- 



34 GAS AND FUEL ANALYSIS 

ping from 20.7 per cent, to 20.4 per cent. Tests showed that 
the oxygen was still being quantitatively absorbed but that 
about 0.3 per cent, of carbon monoxide was being evolved. 
These results confirm Berthelot's statements. According to our 
results 1 c.c. of the reagent absorbs 8.0 c.c. of oxygen. In case 
of doubt concerning the reagent it should be tested on air and 
should be rejected unless it absorbs 20.6 to 20.8 per cent, of oxygen. 

5. Other Reagents for Oxygen. — Sodium hydrosulfite has 
been recommended by Franzen 1 as a cheaper and better reagent 
than pyrogallol. The solution is prepared by dissolving 50 grm. 
Na 2 S 2 04 in 250 c.c. H 2 and mixing this with 40 c.c. of a caustic 
solution made by dissolving 500 grm. NaOH in 700 c.c. H 2 0. 
Each cubic centimeter of this reagent absorbs 10.7 c.c. oxygen. 
The equation for the reaction is as follows: 

Na 2 S 2 4 +H 2 + = 2NaHS0 3 

The solution is placed in a pipette containing rolls of iron gauze 
to increase the absorbing surface. Franzen states that the 
absorption is complete in five minutes without shaking and pro- 
ceeds almost as rapidly at 4° C. as at room temperature. 
There is no danger of the formation of CO in the process which 
constitutes the greatest objection to pyrogallate. An ammoni- 
acal copper solution was proposed by Orsat 2 as a reagent for 
the absorption of oxygen. He used a cold saturated solution of 
ammonia and ammonium chloride in contact with metallic cop- 
per. Oxygen is readily absorbed and the liquid assumes a blue 
tint. He also called attention to the limitation in the use of 
this reagent caused by the action of the ammoniacal copper salt 
on carbon monoxide. 

Oxygen may be accurately estimated by explosion with 
excess of hydrogen or by combustion with copper and these 
methods will be discussed later. 

6. Carbon Monoxide. — The methods for absorption of CO 
are less satisfactory than for any of the other commonly occurring 
gases. The usual reagent is cuprous chloride Cu 2 Cl 2 which on 
account of its slight solubility in water must be used either in 
acid or ammoniacal solution. The acid solution consists of a 

1 Chem.-Berichte, 39, 2069 (1906). 

2 Annates des Mines, 1875, 490. 



ABSORPTION METHODS 35 

practically saturated solution of cuprous chloride in hydrochloric 
acid of specific gravity of approximately 1.12. Since the acid 
is only a solvent, its exact concentration is immaterial. Com- 
mercial acid may be used. About 150 grm. of the cuprous 
chloride will dissolve in a liter of acid of this concentration. 
This solution of cuprous chloride when pure is perfectly colorless 
but it darkens through slight oxidation as on exposure to the 
air, so that the usual solutions are black. It is possible to keep 
it colorless by placing in the reagent bottle or in the pipette 
copper turnings or copper wire, but it does not increase the 
efficiency of the reagent. If the oxidation proceeds so far that 
the solution becomes green, due to complete oxidation to the 
cupric state, the solution is worthless until it is again reduced 
to the cuprous state. 

The reagent is kept in a double pipette whose third bulb is 
filled with HC1 of sp. gr. 1.12 instead of water so that in case 
the cuprous chloride spills into it, it will not be precipitated. 
The gas which must have been previously freed from unsaturated 
hydrocarbons and oxygen is passed into the pipette and shaken 
for three minutes, then drawn back to the burette and passed 
into a second pipette containing fresh cuprous chloride where 
it is again shaken for three minutes, drawn back and measured. 
The HC1 vapors in the gas may be neglected. There is no 
method of knowing whether the absorption of the CO has been 
complete. The only safe way is to repeat the absorption using 
a fresh solution until the volume becomes constant. Usually 
two absorptions of three minutes each are sufficient. 

The reaction between carbon monoxide and cuprous chloride 
has not been definitely worked out. Jones 1 has shown that 
under certain circumstances a crystalline compound of definite 
composition results — Cu 2 Cl 2 , 2CO. 4H 2 0. In the dilute solu- 
tions present in gas analysis, however, the reagent behaves 
exactly as if it dissolved the carbon monoxide. When a perfectly 
new solution is used the CO will be practically completely 
removed. As the CO in solution increases there comes appar- 
ently an equilibrium between that in the gas and that in the 
solution, with the result that the absorption is incomplete. If 
a gas with only a small amount of CO is brought in contact 

1 Am. Chem. Jour., 22, 287. 






36 GAS AND FUEL ANALYSIS 

with a solution which has absorbed much, the gas will increase 
in volume due to CO given up by the solution. Each cuprous 
chloride pipette should bear a label on which should be recorded 
the number of cubic centimeters of carbon monoxide which has 
been absorbed. When it has absorbed more than 10 c.c. it is 
not safe to rely on the results. In practice the analyst should 
have two pipettes for cuprous chloride, one, which has absorbed 
considerable carbon monoxide, to be used first, and another, 
which should be kept almost entirely fresh to follow the other. 
When this second pipette has absorbed 10 c.c. of CO it should 
be used as the first pipette and the former first pipette should 
be emptied and refilled with fresh reagent. The solution may 
be regenerated if desired by boiling it for half an hour in a flask 
containing some metallic copper and provided with a reflux 
condensor to prevent much loss of acid. The feebly held CO is 
driven off by the boiling and any oxidized solution is reduced to 
the cuprous state again. 

The ammoniacal solution is made by suspending about 150 
grm. of cuprous chloride in a liter of distilled water into which 
ammonia gas is passed until the liquid becomes a pale blue color. 
The ammoniacal solution slowly regenerates itself on standing, 
the CO becoming oxidized to (NH 4 ) 2 C03 and a mirror of metallic 
copper depositing. The NH 3 gas must be removed by an acid 
pipette before the correct amount of CO absorbed may be read. 

Carbon monoxide may be estimated by explosion or combus- 
tion as described in the next chapter. Minute amounts of it 
may be estimated by the I2O5 method given in Chapter VI on 
"Exact Gas Analysis." 

7. Absorption of Hydrogen. — Hydrogen may be absorbed by 
palladium sponge superficially oxidized to palladous oxide, 
according to the method 01 Hempel. It is necessary to re- 
generate the palladium after each experiment and the reaction 
is prevented by small amounts of carbon monoxide, hydrochloric 
acid and other constituents so that it is not a method which has 
found much favor. 

A solution of palladous chloride as prepared by Campbell and 
Hart 1 is a better reagent. It is used as an almost neutral 1 per 
cent, solution prepared by dissolving 5 grm. palladium wire in 

l Am. Cham. Jour., 18, 294 (1896). 



ABSORPTION METHODS 



37 



30 c.c of HC1 to which is added 1 or 2 c.c. HN0 3 . The solution 
thus prepared is evaporated just to dryness on the water bath, 
redissolved in 5 c.c. of HC1 (sp. gr. 1.20) and 25 or 30 c.c. of 
water, warmed till solution is complete and diluted to 750 c.c. 
It is placed in a simple Hempel . pipette made to be readily 
detachable from its frame so that the bulbs may be placed in a 
water bath. The first bulb of the pipette should have a capacity 
of at least 150 c.c. to allow for expansion of the gas and water 
vapor when the solution is warmed. The gas freed by the usual 
methods from C0 2 , C n H 2n , 2 and CO, and containing H 2 , 
CH 4 and N 2 is passed into the pipette and the water from the 
burette passed over to seal the capillary of the pipette. A screw 
clamp is placed on the rubber connecting tube and the pipette 
disconnected from the burette and placed in a water bath at 
50° C. for an hour and a half. A higher temperature does no 
harm provided it does not expand the gas so much as to cause 
it to bubble out of the first bulb or to leave only a small amount 
of reagent in contact with the gas in the first bulb. The hydrogen 
reacts with the palladium chloride forming metallic palladium 
and HC1. The total decrease in volume is reported as hydrogen. 
The reagent may be counted on to absorb one-third of its volume 
of hydrogen completely in an hour and a half. Larger quanti- 
ties will be absorbed more slowly. It is readily regenerated by 
rinsing from the pipette, evaporating just to dryness on the 
water bath, dissolving in 5 or 6 c.c. HC1 and 4 or 5 drops of 
HNO3 and again evaporating. The dry palladous chloride is 
dissolved by adding 2 c.c. cone. HC1 and a small amount of 
water and is then diluted to its original volume. The method 
is accurate and satisfactory. Carbon monoxide and other 
reducing gases behave like hydrogen and must be removed pre- 
vious to the test but hydrocarbons of the methane series are 
not affected. The chief objection to the method lies in the time 
consumed which makes it frequently necessary to correct the 
gas volumes for change in room temperature and barometric 
pressure. A memorandum should be made of the temperature 
of the burette jacket and of the barometric pressure before and 
after the test and corrections made if necessary. 

Paal and Hartmann 1 recommend a solution of colloidal 

1 Chem. Berichte, 43, 243 (1910). 



38 GAS AND FUEL ANALYSIS 

palladium made by dissolving 2.44 grm. collodial palladium 
manufactured according to Paal's process by Kaile ( = 1.5 grm. 
palladium) and 2.74 grm. of sodium picrate in enough water to 
bring the volume to 130 c.c. Gaseous hydrogen dissolves in the 
aqueous palladium solution and reduces the picric acid. Hempel 1 
has made a critical study of this method and reports that 
a solution prepared in this manner will absorb in 15 minutes 

when freshly prepared 21.2 c.c. H 2 per 1 c.c. reagent, 
after 79 days 16.2 c.c. H 2 per 1 c.c. reagent, 

after 1 year 1.6 c.c. H 2 per 1 c.c. reagent. 

He states that a fresh solution may be safely trusted to absorb 
completely 7.2 c.c. H 2 per centimeter reagent in three minutes 
if heated to the temperature of the blood. He advocates the 
preparation of the solution in small quantities and its use in a 
pipette filled mainly with mercury. A disadvantage attending 
the use of the reagent is the persistent foam which results after 
shaking and which must be allowed to subside before the volume 
of the gas is read. A few drops of alcohol at once dissipate 
the foam but spoil the reagent for further use. When alcohol is 
used the pipette must be carefully cleaned before another 
experiment. 

In using this method the gas must first be freed from oxygen 
which is caused to unite with the hydrogen by the palladium, 
from unsaturated hydrocarbons which form addition products 
with the hydrogen, and from carbon monoxide which retards 
the absorption of the hydrogen. Bromine is recommended as 
the absorbent for the unsaturated hydrocarbons as it removes 
compounds of arsenic and phosphorus which might retard the 
catalytic action. Alkaline pyrogallate is advised for absorption 
of oxygen as phosphorus fumes affect the palladium. An 
ammoniacal solution of copper chloride is preferred to the acid 
solution. 

8. General Scheme of Analysis. — Fig. 9 shows the apparatus 
ready for the analysis. The details concerning the individual 
steps of the process were given in Chapter II but it is well to 
recapitulate the important points in connection with the general 

1 Zeit. Angewandt. Chem., 25, 1843 (1912). 



ABSORPTION METHODS 



39 



scheme of analysis. The water of the burette is saturated with 
gas similar to that which is to be analyzed and a sample of ap- 
proximately 100 c.c. is then drawn in and the volume read at 
atmospheric pressure after three minutes have been allowed to 
elapse so that the surplus water will have drained from the bur- 
ette walls. Any needed correction for burette error is to be 
applied to this reading. The caustic soda pipette is to be con- 




'I n .1 ■""! r 

Fig. 9. — Assembled apparatus for gas analysis. 



nected to the burette, and the gas passed into it and allowed to 
remain with gentle shaking for three minutes. CO2 is absorbed, 
as well as H 2 S, S0 2 etc., the whole being usually reported as C0 2 . 
The gas is drawn back into the burette and while waiting for the 
excess water on the burette walls to run down, the capillary 
connecting tube is flushed out and the bromine water pipette 



40 GAS AND FUEL ANALYSIS 

is connected. The volume in the gas burette is then read, and 
the gas passed into the bromine water where it is shaken for three 
minutes. It is drawn back to the burette, and at once passed 
into the caustic pipette where it is shaken one minute to re- 
move bromine fumes. It is then drawn back into the burette 
and the decrease in volume reported as unsaturated hydrocar- 
bons. The gas is next passed into the phosphorus pipette. 
White smoke at once appears. If it does not, it is a sign that 
some retarding catalyzer is present, usually removable by an- 
other treatment with bromine water. Following the estimation 
of oxygen comes that of carbon monoxide with cuprous, chloride 
either acid or ammoniacal, preferably acid unless hydrogen is 
to be absorbed by palladium. Two cuprous chloride pipettes 
must be used in series, the second one containing almost fresh 
reagent. The residue from this absorption consists of hydrogen, 
hydrocarbons of the paraffine series and nitrogen. The hydrogen 
may be absorbed by palladium as outlined in this chapter but it 
is more common practice to estimate the hydrogen and hydro- 
carbons by combustion. The methods are discussed in the next 
chapter. 



CHAPTER IV 

EXPLOSION AND COMBUSTION METHODS FOR 

HYDROGEN, METHANE, ETHANE 

AND CARBON MONOXIDE 

1. Available Methods.— Hydrogen and carbon monoxide may 
be estimated by absorption as indicated in the preceding chapter. 
They may also be estimated after oxidation to water or carbon 
dioxide. There are no satisfactory absorbents for methane and 
ethane and so these gases are always estimated indirectly after 
oxidation. The oxidizing agent may be gaseous oxygen and the 
reaction may be violent as in explosion methods or it may be 
quiet combustion. There may even be combustion of hydrogen 



Platinum 
Wire, 



Fused in-- 




Extra thick 
Wall 



Stop Cock, 2mm. 
Bore 

<3mm. Internal 

Diameter 

Fig. 10. — Detail of explosion pipette. 

and carbon monoxide with the aid of a catalyzer in the presence 
of methane which remains unchanged. The oxidizing agent may 
also be an oxide, especially copper oxide, and here again there 
may be fractional combustion. The most rapid method and 
the one most frequently used is that of explosion. 

2. Apparatus for Explosion Analysis. — The analysis by ex- 
plosion is carried out in a stout glass vessel provided with elec- 
tric connections across whose terminals a spark may be passed 
to cause the explosion. The shape and dimensions of the appa- 
ratus may vary. The form which has given good satisfaction 

41 



42 GAS AND FUEL ANALYSIS 

in the gas laboratory at the University of Michigan for a number 
of years 1 is shown in Fig. 10. It is a modification of the Hempel 
pipette and differs from it principally in the arrangement of the 
electric terminals and in the incorporation of an explosion guard 
in the stand. 

In the older forms of pipette the explosion was induced by a 
spark made to jump a gap between two platinum wires sealed 
through the glass of the narrowed upper part of the bulb. When 
the interior of the bulb became wet as frequently happened the 
electric current would sometimes travel around the wet wall 
instead of sparking across the gap, and it was not possible to 
obtain an explosion. Gill 2 modified the bulb by introducing one 
of the wires through a ground glass joint at the bottom of the 
pipette. This was a valuable modification because it made 
the creeping distance so long that the spark was compelled to 
jump the gap, but the ground glass was difficult to keep tight. 
The form here described introduces the wire from the bottom but 
adopts a simple method of sealing which is very satisfactory. 
The lower wire which should be stiff (and may be of nickel about 
1 mm. in diameter) is pushed through the open lower end of 
the pipette and sealed by sucking molten sealing wax into the 
pipette almost to the level of the tee. As the sealing wax 
hardens the wire may be moved to adjust the spark gap to the 
desired dimensions. No difficulty has been experienced in 
making this joint tight. The explosion pipette and its stand 
are shown in Fig. 11. The bulb is enclosed in a box open at 
the top and with a plate glass window in front, so that the 
operator can observe the explosion in perfect safety. The bot- 
tom of this box has an irregular opening sawed in it so that the 
pipette as shown in Fig. 10 may be lowered into place. The bulb 
sits in a cup shaped hollow of the shelf which may be padded 
with wet asbestos paper if necessary to make it fit well. 

The weight of the mercury renders other fastening for the bulb 
unnecessary but the capillary is fastened to the rib behind it by 
a loop of fine copper wire passing through holes drilled in the rib. 
The strain of the rubber tube filled with mercury is taken off the 
glass tee by a ring below the shelf into which the rubber tube is 

1 White and Campbell, /. Am. Chem. Soc, 27, 734 (1905). 

2 J. Am. Chem. Soc, 17, 771 (1895). 



EXPLOSION AND COMBUSTION METHODS 



43 



wedged firmly by a split cork. The rack for the levelling bottle 
is higher than the tee of the pipette so that when the bottle is in 
the rack the mercury in the rubber tube is under pressure whereas 
if the mercury bottle were sitting on the base of the stand there 
would be a partial vacuum within the rubber tube. This may 
seem immaterial, but it must be remembered that all rubber is 
porous and that bubbles of air sucked into the rubber tube are 
certain to make their way up into the pipette and be measured 




Fig. 1 1 .—Explosion pipette and stand with protecting screen. 

as part of the gas in it. Fine copper wires soldered to the elec- 
trode terminals of the pipette pass to the binding posts on the 
stand. The fine platinum electrode is liable to be cut if it is 
bent back and forth where it is sealed through the glass and to 
protect it the copper wire from the upper electrode is brought 
smoothly up to the capillary and tied there firmly with thread. 
The design of the stand is such that if a bulb breaks a new bulb 
may be inserted without trouble if it has even approximately the 
dimensions of the old one. The method of connecting this pipette 
to the burette and of transferring the gas is the same as for other 



44 GAS AND FUEL ANALYSIS 

pipettes. This pipette is filled with mercury, since under the 
high pressure developed the solubility of the gases in water 
becomes large enough to cause appreciable error. An induction 
coil capable of giving a half inch spark together with its bat- 
tery is necessary. A coil giving a large spark such as is given 
by the automobile sparkers is much better than a coil giving a 
thin high voltage spark. 

3. Manipulation in Explosion Analysis. — In the explosion proc- 
ess a sample of gas previously freed from carbon dioxide, oxygen, 
unsaturated hydrocarbons and usually carbon monoxide is drawn 
into the burette and measured. Its volume may vary from 8.0 
c.c. with pure methane to 50 c.c.with gases containing high per- 
centages of nitrogen. Air sufficient to fill the burette is then 
drawn in. The burette is connected to the pipette as usual, 
care being taken to have the rubber connections in good'condition 
and firmly wired, and the mixture is passed into the explosion 
pipette, the water of the burette being run over through the cap- 
illary of the pipette until the capillary is full. This water in the 
capillary acts as a cushion, preventing the force of the explosion 
from blowing up the rubber connections. The gas in the 
explosion pipette is brought to atmospheric pressure by means 
of the levelling bottle, the stopcock is closed, and the levelling 
bottle replaced in its rack. It is advisable to shake the pipette to 
ensure thorough mixing of the gases, for diffusion proceeds some- 
what slowly. The gas is exploded by a spark from the induction 
coil. If the gas consists mainly of hydrogen there is usually 
no visible flame although a slight tremor of the mercury may be 
observed. If the gas contains much hydrocarbon a flash of flame 
may usually be seen. It is not advisable to spark the mixture 
more than a second as some nitrogen will unite with the oxygen 
at the temperature of the spark forming oxides of nitrogen with 
decrease of volume and erroneous results. The explosion com- 
pleted, the gas is again brought to atmospheric pressure by means 
of the levelling bottle, and then brought back into the burette and 
measured. If there has been marked contraction, the next step 
is to pass the gass into caustic solution and determine if there 
has been formation of carbon dioxide. 

If the decrease in volume after explosion was less than 12 
c.c. it is almost certain that the explosion was incomplete. If 



EXPLOSION AND COMBUSTION METHODS 



45 



there was no decrease in volume it is not safe to assume that no 
combustible gas was present, for it may have been present in such 
a small proportion that the mixture was not explosive. The 
proper procedure in either case is to add about 10 c.c. of pure 
hydrogen made by the action of caustic potash on metallic 
aluminum and explode a second time. The addition of this 
amount of hydrogen ensures complete explosion. After allow- 
ance for the contraction due to the added hydrogen, the composi- 
tion of the original gas may be calculated as explained later. 

It is advisable to determine roughly the amount of oxygen 
remaining after the explosion so that there may be no doubt 
that an excess was present. 

4. Oxidation of Nitrogen as a Source of Error. — Almost all 
technical gases contain nitrogen as do also commercial forms of 
oxygen. Bunsen first noted that nitrogen and oxygen react at 
the temperature of the electric spark or of an explosion flame to 
form small amounts of various oxides of nitrogen whose volume 
is less than that of the reacting gases and which combine with 
caustic. The formation of oxides of nitrogen leads, therefore, to 
an erroneously high contraction after explosion and to an errone- 
ously high figure for C0 2 due to explosion. The error is discussed 
more fully in Chapter VI on Exact Gas Analysis but it cannot be 
altogether neglected in technical work. The error increases with 
higher flame temperatures and the simplest way to keep it within 
reasonable limits is to dilute the reacting gases with some inert 
gas such as nitrogen or excess of oxygen. The volume of the 
gases participating in the explosion (combustible gas + theoret- 
ical volume oxygen) should be from one-third to one-fifth that 
of the non-exploding gases (nitrogen + excess oxygen). It will 
be seen that 12 c.c. H 2 + 6 c.c. 2 require to be diluted with from 
54 to 90 c.c. nitrogen or oxygen and that 8 c.c. CH 4 + 16 c.c. 
2 require at least 72 c. c. of diluting gases. 

The explosion of large samples of gas mixed with commercial 
oxygen, a method proposed by Hinman and endorsed by Gill, 1 
involves much greater danger of blowing up the pipette and be- 
cause of the higher temperature of explosion, tends to cause 
a larger formation of oxides of nitrogen from the nitrogen 
necessarily present. 

ij. Am. Chem. Soc, 17, 987 (1895). 



46 GAS AND FUEL ANALYSIS 

5. Accuracy of Explosion Methods. — The necessity of diluting 
the exploding gases to avoid oxidation of nitrogen restricts the 
size of a sample of a rich gas like illuminating gas to about 10 
c.c. With this small sample each 0.1 c.c. error in reading means 
1.0 per cent. A greater accuracy can therefore not be expected 
except by averaging a number of analyses. It may be considered 
safe to rely upon a single analysis for the various gases deter- 
mined by absorption, but explosion analyses should always be 
made in duplicate. The main portion of the gas after the 
absorption should be stored in a gas holder to be drawn upon for 
subsequent check analyses. 

6. Hydrogen by Explosion. — If hydrogen is the only com- 
bustible gas taking part in the explosion its volume may be 
calculated from the contraction after explosion according to 
the following equation : 

2H 2 +0 2 = 2H 2 

2 + 1 =2 or 

Expressed in volumes this means that two volumes of hydrogen 
combine with one volume of oxygen to form two volumes of 
water vapor. Since, however, the gas after explosion cools 
again to the temperature of the burette water and is the same 
as before explosion, and since it was saturated with water 
before explosion, the additional water formed must all condense. 
For our purposes, therefore, two volumes of H 2 react with one 
volume of 2 with complete disappearance of the reacting gases. 
Under these circumstances when hydrogen is the only exploding 
gas, two-thirds of the resulting contraction will be the volume 
of the hydrogen exploded. 

7. Hydrogen and Methane by Explosion. — Methane combines 
with two volumes of oxygen to form carbon dioxide and water 
according to the following equation: 

CH 4 +20 2 = C0 2 + 2H 2 
1+2 =1+0 

The volumetric relations are expressed by the figures of the 
equation, one volume of methane uniting with two of oxygen 
to form one volume of carbon dioxide, and two of water vapor 



EXPLOSION AND COMBUSTION METHODS 47 

which condense and disappear as explained in the preceding 
paragraph. The result of the explosion, therefore, is that there 
is a contraction of two volumes for every one volume of methane 
and the formation of a volume of carbon dioxide equal to the 
methane. 

It is possible to determine the proportion of hydrogen and 
methane present in a gas mixture by explosion with air. The 
volume of carbon dioxide resulting from the explosion equals 
the volume of the methane. The contraction due to the methane 
is twice the volume of the methane and the difference between 
this contraction in volume and the total contraction is the 
contraction due to the explosion of hydrogen. In accordance 
with the preceding section two-thirds of this contraction is 
hydrogen. The following example will serve as an illustration 
of the method of calculation. 



Sample of illuminating gas 99 . 5 c.c. 

Volume after absorption of C0 2 , C n H 2n , 2 , CO 85.2 

Sample for explosion 10.3 

Air to 97.6 

After explosion, volume 80 . 1 

Contraction 17 . 5 

After KOH, volume 74.9 

Vol. C0 2 formed ' 5.2 

After phosphorus, volume 69 . 4 

Vol. excess oxygen . . . 5.5 

Calculation 5.2 c.c. C0 2 = 5.2 c.c. CH 4 

Contraction due to 5 . 2 c.c. CH 4 = 2X5.2 = 10.4 
Contraction due to hydrogen =17.5—10.4 = 7.1 
Hydrogen = 2/3X7.1=4.7 
Vol. CH 4 = 5.2 
Vol. H 2 = 4.7 
Vol. N 2 by diff. 0.4 



10.3 



or o y 1 00 
Per cent. CH 4 = 5.2X 1Q "3x99 5 = 43 - 1 

, « 85.2X100 nn n 
Percent. H 2 -i.rx^^-w.o 

Percent. N, _Q.4Xjgfjg|- 8.8 



48 GAS AND FUEL ANALYSIS 

The ratio of exploding to non-exploding gases in the above 
illustration may be calculated as follows: 

Exploding gases 5.2 c.c. CH 4 + 10.4 c.c. 2 = 15.6 
4.7 c.c. H 2 +2.35c.c. O 2 =7.05 



Exploding gases 22 . 65 

Non-exploding gases 97 . 6 - 22 . 65 = 74 . 95 
exploding gases 22.65 1 
non-exploding gases 74.95 ~~ 3.3 

The excess of oxygen is calculated from the volume of air 
taken for explosion, =97.6—10.3 = 87.3 c.c. air with 20.9 per 
cent. 2 = 18.24 c.c. O2 available. Used for combustion, 
as above, 10.4+2.35 = 12.75 c.c. Excess oxygen = 18.24 — 
12.75 = 5.49 c.c, which checks with the 5.5 c.c. found by direct 
experiment. 

8. Carbon Monoxide, Hydrogen and Methane by Explosion.— 
The composition of a gas mixture containing CO, H 2 , and CH 4 
may be determined by a single explosion ir in addition to the 
contraction and CO2 the oxygen used in the explosion is also 
determined. 

There are various methods of calculation, that given by 
Noyes and Shepherd 1 being as follows: 

1. Gas taken = CH 4 +CO + H 2 + N 2 

2. Contraction =2CH 4 +|CO+fH 2 

3. Oxygen consumed = 2CH 4 +§CO + |H 2 

4. C0 2 iormed = CH 4 +CO 

Hence H 2 = Contraction — 2 consumed. 
CO = | (2C0 2 +iH 2 -0 2 consumed) 
CH 4 = C0 2 -CO 

N 2 = Total gas-(H 2 +CO+CH 4 ). 

The oxygen consumed is calculated by determining the residual 
oxygen and deducting this from the volume of oxygen introduced 
as air whose percentage of oxygen is assumed to be 20.9. 

This method is more rapid than the usual one in which the 
CO is absorbed by Cu 2 Cl 2 , and it has no systematic errors, 
provided the dilution is great enough to avoid oxidation of 
nitrogen. It will, except in expert hands, be found less reliable 

1 /. Am. Chem. Soc. 20, 345 (1898). 



EXPLOSION AND COMBUSTION METHODS 



49 



than the usual method of absorption of CO and explosion of H 2 
and CH 4 because each value calculated is dependent on the 
accuracy of three successive operations instead of two. 

9. Quiet Combustion of a Mixture of Oxygen and Combust- 
ible Gas. — Various attempts have been made to do away with 
the explosion pipette by causing the gas to burn gradually. 
Coquillion 1 in 1876 proposed to estimate small amounts of 
hydrocarbons in the air from mines by placing within a pipette 
a spiral of platinum or palladium wire. The mine air was in- 
troduced into the pipette, the spiral was to be heated to redness 
and, the amount of combustible gas being below the explosive 
ratio, the hydrocarbons were to be gradually burned. He 
recommended that for technical gases where there was danger 
of explosion the platinum spiral be placed in a small bulb blown 




Fig. 12. — Quartz combustion tube with platinum spiral. 



in the capillary tube between the burette and pipette. The 
mixture of gas and air was measured in the burette, and then 
passed through the capillary over the glowing spiral. The 
capillary tube was supposed to be adequate to prevent the 
explosion from flashing back into the burette. Hempel 2 has 
improved this latter apparatus by placing the platinum spiral 
in a quartz tube between two glass capillary tubes. His arrange- 
ment as modified by the author is shown in Fig. 12 where AB 
represents a tube of transparent quartz about 4 mm. internal 
diameter and 125 mm. long, at each end of which are glass cap- 
illary tees connected to it by rubber tubing. Through each tee 
runs a stout nickel wire connected by a spiral of fine platinum 
wire. The nickel wires are sealed into the glass capillaries by 
sealing wax drawn into the enlarged ends of the capillaries. The 
apparatus may therefore be readily repaired if the platinum 

1 Compter rendus, 83, 394; 84, 458 and 1503. 

2 Zeit. angewandt. Chem., 25, 1841 (1912). 



50 GAS AND FUEL ANALYSIS 

wire becomes burned out. The nickel wires should be so large 
that they almost fill the capillary tube which should be of about 
1 mm. internal diameter. They will then not be heated per- 
ceptibly by the passage of an electric current sufficient to heat 
the platinum wire to redness and will by their cooling action 
help to prevent the explosion from flashing back into the gas 
burette. If the mixture of gas and air is passed slowly over the 
platinum spiral the temperature will not rise above a fair red 
heat and there will be little danger of formation of oxides of 
nitrogen, hence there is no need of diluting the gases with so 
much air as is necessary in the explosion process and therefore a 
larger sample of gas may be used. It is not safe, however, to 
take a large sample of gas and dilute it with pure oxygen, for the 
capillary tube cannot be relied upon to prevent an explosion 
flashing back into the burette when a very explosive mixture is 
used. 

The inaccuracy of the usual explosion methods led Dennis 
and Hopkins 1 to devise a process of combustion whereby a 
large sample of gas might be quietly burned in pure oxygen. 
The combustion pipette consists of a pipette such as is used for 
phosphorus with its second bulb cut off and a levelling bottle 
for mercury connected. The ignition wire in the form of a 
platinum coil or grid is placed within the pipette immediately 
under the gas inlet and connected to two heavy wires which, 
insulated from each other, pass through the rubber stopper at 
the bottom of the pipette and are fastened to binding posts. 
The diameter and length of the platinum ignition wire must be 
chosen with reference to the electric circuit so that it will be 
easily heated to redness and its temperature controlled without 
the need of cumbrous rheostats. The conducting wires within 
the pipette may be of platinum or one of the non-rusting nickel- 
chromium alloys and should be at least 1 mm. in diameter. 

The manipulation is as follows. The full volume of gas 
remaining after absorption of oxygen, consisting of CO, H 2 , 
CH 4 and N 2 is transferred to the combustion pipette and a 
clamp is screwed onto the rubber connecting tube at the tip of 
the burette so that the pipette may be disconnected from the 
burette. The burette is filled with oxygen free from CO2 and 

1 J. Am. Chem. Soc, 21, 398 (1899). 



EXPLOSION AND COMBUSTION METHODS 51 

of known purity and reconnected to the pipette, but the stop- 
cock of the burette is kept closed. The levelling bottle of the 
pipette is placed at such a height that the gas in the pipette is 
under slightly diminished pressure and the electric ignition wire 
brought to incandescence. The stopcock on the burette is 
now opened and a slow stream of oxygen passed into the pipette. 
A slight flash is usually noticeable as ignition takes place and 
the platinum wire glows more brightly so that it may be necessary 
to interpose more resistance in the heating circuit. The volume 
of gas in the pipette may either increase or decrease and the 
height of the levelling bottle must be varied accordingly. It is 
usually necessary to periodically increase the external resistance 
to prevent the platinum wire from burning out as the hydrogen 
originally present gives way to water vapor. After the oxygen 
is all passed into the pipette, the current is interrupted, the gases 
allowed to cool and the CO, H 2 and CH 4 determined as in § 8. 

The great advantage of this process lies in the large sample 
and the consequent diminution of the error of observation. It 
requires a special pipette, which is, however, easily constructed, 
a source of electric current and a controlling rheostat. The 
manipulation is somewhat complicated and it has been the 
author's experience that novices usually wish that nature had 
provided them with an extra pair of hands. The error due to 
oxidation of nitrogen has been found by the author 1 to be fully 
as large in this process as in the explosion process. The subject 
is discussed more fully in Chapter VI. Hempel 2 also reports 
unfavorably on this process on account of the formation of oxides 
of nitrogen when combustion is continued long enough to ensure 
oxidation of all the methane. 

10. Fractional Combustion with Palladinised Asbestos. — The 
well known power of palladium to bring about the union of hy- 
drogen and oxygen at low temperature has long been made use 
of as a means of separating hydrogen from methane. The use 
of palladinised asbestos is due to Winkler. The asbestos is 
prepared by soaking a small amount of selected long fibered 
asbestos in a concentrated solution of palladous chloride prepared 
according to § 7 of Chapter III. The fibers are to be kept as 

1 J". Am, Chem. Soc, 23, 477 (1901). 
*Zeit. Angewandt. Chcm., 25, 1841 (1912). 



52 GAS AND FUEL ANALYSIS 

nearly parallel as possible and after saturation are to be dried 
and ignited at a very dull red heat when the chloride will de- 
compose leaving the fibers coated with metallic palladium and 
possibly palladous oxide. A bundle of two or three of these 
single fibers about an inch long is introduced into the end of a 
straight capillary glass tube about 1 mm. internal diameter and 
eight inches long, and brought to the middle of the capillary by 
suction on the opposite end of the tube. A drop of water on 
the asbestos makes it move more freely. The capillary is then 
to be dried and bent to the usual form for connecting the burette 
and pipette. 

In manipulation 20 or 30 c.c. of gas freed from C0 2 , C n H 2n 
and usually CO is mixed with an excess of air and passed through 
the capillary tube containing the palladinised asbestos into a 
pipette containing water. If the asbestos is very active, com- 
bustion may begin without external heat but to make certain 
the tube is heated with a small gas flame or alcohol lamp. It is 
not necessary to heat the tube to redness. A spark frequently 
appears at the end of the asbestos filament when the combustible 
gas first strikes it. This is a sign that the gas is passing too 
rapidly and the speed must be decreased until the spark disap- 
pears. Otherwise some methane will be burned. The gas is 
passed back and forth through the capillary twice and then drawn 
back into the burette and the volume measured. If hydrogen 
alone has been burned two-thirds of the contraction will be the 
volume of the hydrogen as explained in § 6. Carbon monoxide 
will burn as well as hydrogen in this process and where both 
were present, it will be necessary to determine the carbon dioxide 
formed in addition to the contraction. The calculations follow 
from the equations: 

2CO + 2 = 2C0 2 

2 + 1 =2 Contraction = JCO or |C0 2 

2H 2 + 2 = 2H 2 

2+1 =0 Contraction = |H 2 

Therefore C0 2 = CO 

Total contraction •= JCO+|H 2 
H 2 = f (contraction — JCO) 



EXPLOSION AND COMBUSTION METHODS 53 

This method is accurate provided the palladinised asbestos 
is dry and active and the proper temperature is maintained. 
It requires care to prevent any drops of water from getting into 
the capillary. If this happens when the capillary is cold the 
thread of asbestos becomes wet and must be dried thoroughly 
before it is active. If a drop of water gets into the capillary 
while it is hot the glass tube cracks. Very little attention has 
been paid to the possibility of small amounts of foreign gases 
rendering the palladium catalyzer inactive, but from the elaborate 
precautions which are necessary to keep the platinum contact 
substance active in the sulphuric acid manufacture it is evident 
that this possibility should not be ignored. The capillary tube 
should never be heated to redness on account of danger of burn- 
ing methane. The combustible gases are diluted largely with 
air to avoid too intense combustion and also to avoid an ex- 
plosion of the main body of the gas which might be propagated 
through the capillary if the gas mixture were too rich. Dis- 
astrous explosions have been known to result from an attempt 
to burn mixtures of hydrogen and oxygen in this manner. The 
combined volumes of hydrogen and carbon monoxide in the 
sample taken for analysis should not be over 20 c.c. and the 
volume after dilution with air should be almost 100 c.c. This 
method has been investigated by Nesmjelow 1 who emphasizes 
the danger of burning methane if the gases are passed through 
the capillary at a rate faster than one liter per hour. Hempel 2 
has recently reported the results of a study of this process and 
finds that to obtain accurate results the temperature of the 
capillary must not rise over 400° C. and that the gas must be 
passed at a speed of not over 100 c.c. in eight minutes. He rec- 
ommends, as a method of temperature control, that the portion 
of the capillary to be heated rest in a brass trough which in the 
middle is thickened sufficiently to contain a hole deep enough 
for a thermometer bulb. In default of a thermometer a glass 
tube sealed at the bottom and containing a little mercury may 
be inserted in the hole. The boiling of the mercury (358° 
C.) indicates when a sufficiently high temperature has been 
reached. 

1 Zeit. Anal. Chem., 48, 232 (1909). 
2 Zeit. Angewandt. Chem., 25, 1841 (1912). 



54 



GAS AND FUEL ANALYSIS 



11. Fractional Combustion with Copper Oxide. — The com- 
bustion of carbon compounds of all sorts through contact with 
hot copper oxide has been a method long employed by organic 
chemists. Campbell 1 first utilized the principle of fractional 
combustion in gas analysis and determined accurately the mini- 
mum combustion temperature for various gases both with copper 
oxide alone and with palladinised copper oxide. His values 
are as follows: 



Gas 


Initial combustion point 


Pure CuO 


Pd.-CuO 


H 2 

CO 


175-180° C. 
100-105° C. 
315-325° C. 
270-280° C. 
320-330° C. 
No combustion at 455° C. 


80-85° C. 
100-105° C. 
240-250° C. 




220-230° C. 


C 4 H 8 (Iso) 

CH 4 


270-280° C. 



Jaeger 2 first proposed a convenient scheme for utilizing this 
principle in ordinary gas analysis and the method usually bears 
his name. He takes advantage of the wide difference in the 
ignition point of CO and H 2 as compared with CH 4 to separate 
the two gases by fractional combustion. His method with some 
modifications which the author has found desirable is as follows: 

The combustion tube shown at A in Fig. 13 is of hard Jena 
glass or preferably transparent quartz and has an internal 
diameter of about 10 mm. and a length of 200 mm. It is filled 
throughout its middle 100 mm. with granulated copper oxide 
kept in place by wads of asbestos fiber. The open ends of the 
tube are closed by elbows of glass capillary tubing which slip 
within each end of the combustion tube as far as the asbestos 
wads and are held in place by rubber tubing fitting tightly over 
the end of the combustion tube and also over the glass capillary. 
The asbestos shield shown in section at B and in elevation at C 
sits like a saddle over the middle portion of the tube and keeps 
the heat from the rubber connections during combustion. 
The combustion gases pass out the perforations shown in the 
top of the shield. A thermometer standing in the tube of the 

1 Am. Chem. Jour., 17, 688 (1895). 
2 Jour.Gasbehucht, 41,764 (1898). 



EXPLOSION AND COMBUSTION METHODS 



55 



shield with its bulb touching the combustion tube indicates 
the temperature at which hydrogen is being burned. 

The whole volume of the gas from which C0 2 , C n H 2w and 2 
have been removed is used for the analysis. The copper oxide 
tube is connected to the burette on one side and on the other to 
a phosphorus pipette which has been previously filled with air 
and now contains nitrogen. This nitrogen is allowed to flow 
through the combustion tube and out into the air through the 
burette stopcock flushing out the air in the tube and rendering 





Fig. 13. — Quartz combustion tube filled with copper oxide. 

unnecessary the troublesome correction involved in Jaeger's 
original method. The nitrogen is all driven out of the phos- 
phorus pipette, and the water in it blown to a mark arbitrarily 
fixed on the capillary stem of the pipette and the burette stop- 
cock turned so that connection with the outside air is shut off, 
the burette also remaining closed. The gas burner under the 
combustion tube is lighted and adjusted so that the thermometer 
inserted in the jacket and resting on the combustion tube shows 
about 250° C. The expanding nitrogen in the combustion 
tube is free to pass into the phosphorus pipette. When the 



56 GAS AND FUEL ANALYSIS 

combustion tube is hot, the burette stopcock is opened and 
the gas passed slowly into the phosphorus pipette and back 
again so that it has all been exposed twice to the action of the 
copper oxide. A few cubic centimeters of the gas are again 
passed into the phosphorus pipette, the burette stopcock is 
closed and the flame removed. If the combustion tube is of 
glass it must be slowly cooled to room temperature but if it is 
of quartz it may be sprayed with water or wrapped with a wet 
cloth until it again reaches room temperature. As the tube 
cools there is sucked back from the pipette some of the gas 
purposely placed there and when it is thought that the tube 
has reached room temperature the liquid of the pipette is again 
brought to the mark in the capillary which was used at the com- 
mencement of the test. If after adjustment has been made the 
water of the pipette continues to rise in the capillary it is proof 
that the combustion tube has not yet reached room temperature. 
The volume of the gas in the burette is now measured and a 
caustic potash pipette substituted for the phosphorus pipette. 
This requires somewhat careful manipulation for the combustion 
tube is still filled with gas which must not be allowed to diffuse 
into the air. To accomplish the substitution the stopcock of 
the burette is opened and the gas drawn out of the capillary 
of the phosphorus pipette into the burette until the liquid has 
mounted as high as the rubber connecting tube. The glass 
capillaries of the pipette and the combustion tube are separated 
enough to allow a clamp to be screwed on the rubber tube and 
the phosphorus pipette is disconnected and replaced by a caustic 
pipette whose liquid before making the connection is blown 
practically to the top of the capillary by the help of a rubber 
tube attached to the second bulb. With care this substitution 
of one pipette for the other may be made with an error of only a 
few tenths of a cubic centimeter. The carbon dioxide formed 
from the CO is then determined. Since it is not feasible to drive 
all the gas from the combustion tube into the caustic the gas 
should be passed back and forth several times. The method 
of calculation of the H 2 and CO follows from the equations: 

H 2 +CuO = H 2 + Cu 
CO+CuO = C0 2 +Cu 



EXPLOSION AND COMBUSTION METHODS 57 

The metallic copper has practically the same volume as the 
copper oxide. The C0 2 has the same volume as the CO. The 
H 2 completely disappears. Therefore the contraction in volume 
after heating to 250° is equal to. the H 2 , and the C0 2 is equal to 
the CO. 

Methane is estimated by heating the combustion tube to 
redness and slowly passing the gas back and forth into the 
caustic pipette. Methane burns somewhat slowly and it is 
wise to pass it back and forth at least four times. The decrease 
in volume is read after the • combustion tube has been cooled 
as before. The equation for the reaction is: 

CH 4 +4CuO = 4Cu+C0 2 +2H 2 0. 

If the gas had been passed back and forth into a pipette filled 
with water during the combustion there would have been no 
change in volume but since the gas was passed into the caustic 
pipette during the combustion process and the C0 2 was absorbed 
the contraction equals the methane. 

It is assumed in this calculation that CH 4 is the only one of 
the paraffine series present. This is usually the case but natural 
gas, Pintsch gas, carburetted water gas and gas from coal dis- 
tilled below a red heat may contain small proportions of ethane 
and possibly higher homologues. Pentane vapors are present 
in many samples of natural gas. Any two constituents such as 
methane and ethane may be determined by this method if during 
the combustion at a red heat the gases are passed back and forth 
into the phosphorus pipette or other pipette filled simply with 
water and the contraction after combustion measured and then 
the C0 2 determined. The calculation follows from the equations: 

CH 4 +4CuO = 4Cu+C0 2 +2H 2 0. 
C 2 H 6 +7CuO = 7Cu+2C0 2 +3H 2 0. 

In the case of CH 4 , the volume is the same after combustion 
as before. In the case of C 2 H 6 the volume has increased by a 
volume of C0 2 equal to the C 2 H 6 . Any increase in volume after 
combustion is reported as C 2 H 6 and the volume of the C0 2 less 
twice the C 2 H 6 is reported as CH 4 . 

In case pentane is present the increase of volume after com- 



58 GAS AND FUEL ANALYSIS 

bustion is four volumes for each volume of pentane according to 
the equation — 

C 5 H 12 +16CuO = 5C0 2 +6H 2 0. 

It is not usually feasible to distinguish by analysis between 
the various higher hydrocarbons. 

The copper oxide has been partially reduced to metallic copper 
in the combustion and must be re-oxidized by drawing air through 
the red hot tube. This may be done very conveniently by means 
of an aspirator since no attention on the part of the analyst is 
required. 

This method is perhaps the most accurate of the technical 
methods for the estimation of CO, H 2 and CH 4 and is to be com- 
mended because it does not involve any special equipment 
which cannot be made by the analyst himself. It is somewhat 
slower than the explosion methods but if a quartz tube is available 
it is not a tedious process. A quartz tube is highly desirable since 
glass tubes always break after a time and in breaking usually 
spoil the analysis. There is no danger of oxidation of nitrogen 
as in the other methods and a large sample of gas may be taken 
thus reducing the errors of observation to a minimum. The 
greatest liability to error comes from incomplete combustion of 
the hydrocarbons. Ethane is especially difficult to burn and 
it is desirable to repeat the combustion on the gas residue after 
the C0 2 has been absorbed to make sure that there is no further 
formation of C0 2 . 

12. Nitrogen. — There is no desirable method for the direct 
determination of nitrogen, which is always taken by difference. 
This is very unsatisfactory since, although some of the errors 
in analysis may compensate each other, there is a tendency in a 
long analysis for them to pile up on the nitrogen. 

The Jaeger method of combustion with copper oxide just 
described allows all of the gases other than nitrogen to be re- 
moved in a single process and affords a valuable check on the 
accuracy of the longer anaylsis. A sample of 100 c.c. of the gas 
to be analyzed is passed through the combustion tube at red 
heat and into caustic. The C0 2 , CO, H 2 , and C n H m will all 
disappear in the process as will also the oxygen if it is present in 



EXPLOSION AND COMBUSTION METHODS 59 

only small amount. The residue will be nitrogen and possibly 
oxygen which may be removed by phosphorus. 

13. Form of Record of Gas Analysis. — There may of course 
be great variation in methods of keeping records of gas analyses. 
The record should in every case however be full enough to show 
every step of the operation. The following record is given as a 
sample. 

ANALYSIS OF ILLUMINATING GAS 

at Chemical Laboratory, University of Michigan, Sept. 9, 1907 



Sample 


99.4-0.3=99.1 c.c. 






After KOH 


97.4 


C0 2 =2.0 c.c. = 


= 2.0% 


After Br 2 


92.6 


C 2 H 4 , etc., 4.8 c.c. 


4.8 


After P 


92.2 


2 0.4 c.c. 


0.4 


After Cu 2 Cl 2 


84.8-0.3=84.5 


CO 7.4 c.c. 


7.5 


First explosion: 








Sample 


9.4-0.3= 9.1 






Air to 


97.9-0.3=97.6 






After explosion 


83.0 


Contraction =14.9 




After KOH 


79.2 


C0 2 = 3.8 




After P 


71.0 


Excess 2 =8.2 




Calculations : 









Factor to give percentage n i n/Q oTT = 9.37 

CH 4 = 3.8X9.37 =35.6% 

H 2 =2/3(14.9-2X3.8)9.37 =45.6% 

N 2 = [9.1-(3.8+4.87)]9.37 = 4.0% 

Exploding gases: 

3.8 c.c. CH4+7.6 c.c. 2 =11.4 c.c. 

4.9 c.c. H 2 +2.4 c.c. 2 = 7.3 c.c. 



18.7 

Non-exploding gases: 

97.6-18.7 78.9 

^ . non-exploding 78.9 . „ 

Ratio j—t: = ^-^==4.2 

exploding 18.7 

Second explosion: 

Sample 9.2-0.3= 8.9 c.c. 

Air to 95.0-0.3=94.7 

After explosion 80 . 4 Contraction 14 . 6 

After KOH 76.7 C0 2 3.7 

After P 70.0 Excess 2 6.7 



60 



GAS AND FUEL ANALYSIS 



Calculations : 

Factor to give percentage q Qya cTT =9.58 

CH 4 =3.7X9.58 =35.4% 

H 2 =2/3(14.6-2X3.7)9.58 =46.0 

N 2 =[8.9-(3.7+4.8)]9.58 = 3.8 

Exploding gases: 

3.7 c.c. CH4+7.4 c.c. 02 = 11.1 c.c. 

4.8 c.c. H 2 +2.4c.c. 2 = 7.2 



18.3 



Non-exploding gases: 



94.7-18.3 




= 76 


.4 




_ . non-explodin 


g 


76 


•4 „ „ 




Ratio , ,. 

exploding 




~Y8 


; 3 =4 - 2 




Summary of analysis: 












I 




11 


Average 


C0 2 


2.0 






2.0% 


C0H4, etc., 


4.8 






4.8 


o 2 


0.4 






0.4 


CO 


7.5 






7.5 


CH 4 


35.6 




35.4 


35.5 


H 2 


45.6 




46.0 


45.8 


N 2 


4.0 




3.8 


3.9 



99.9% 



CHAPTER V 

VARIOUS TYPES OF APPARATUS FOR TECHNICAL GAS 

ANALYSIS 

1. Introduction. — Chapter II describes the apparatus which 
the author believes best adapted to technical gas analysis and 
gives detailed directions for its manipulation. The present chap- 
ter will describe various other forms of technical apparatus 
especially those which first embodied valuable principles. The 
number of modifications is legion and no attempt will be made to 
even enumerate them. The order of description will in general be 
historical. 

2. Schlosing and Rolland's Apparatus. — Perhaps the earliest 




Fig. 14. — Schlosing and Rolland's apparatus. 

successful attempt to devise an apparatus for the rapid analysis 
of industrial gas was that of Schlosing and Rolland 1 who de- 
vised a simple apparatus which foreshadowed closely the modern 
type. Their apparatus apparently attracted little attention 
1 Annates de. Chim., Series 4, t.14, 55 (1868). 



62 GAS AND FUEL ANALYSIS 

partly because its description was embodied in a long article on 
the ammonia-soda process whose title did not contain any ref- 
erence to gas analysis. The original cut of their apparatus is 
reproduced as Fig. 14 as it still may serve as a model for a chemist 
who has to improvise his own apparatus. The following descrip- 
tion of the apparatus is taken from the original work. In the 
upper left hand corner of the cut are seen four lead pipes of small 
diameter coming from various pieces of apparatus in the plant. A 
rubber tube d connects any one of these with the copper tube t 
to which is attached an aspirator. The burette a terminates at 
the top in a tee of almost capillary tubing, one arm of which con- 
nects to the gas supply through the cock r and the other to the 
pipette b. No mention is made of a clamp on the rubber tube 
between a and b but necessarily such must have been used. To 
draw a sample of gas the cock r is opened and the levelling bottle 
c is raised until the water fills the burette and reaches r. The 
gas formerly in the burette is now in the pipe t out of which it is 
swept by the stream of gas which is constantly flowing. The 
bottle is then lowered until the gas has passed below the 100 mark. 
The aspirator is stopped, the rubber tube d disconnected and the 
bottle raised, r being again opened until the level of the water in 
the burette is at 100 and is at the same time coincident with the 
level of the water in the levelling bottle. The burette will then 
contain 100 volumes of gas at atmospheric pressure. The gas 
is then passed back and forth into the absorption pipette b filled 
with caustic potash and containing glass tubes to increase the 
absorptive surface. The volume in the burette is then read as 
before and the decrease in volume reported as C0 2 . 

3. Orsat's Apparatus. — The original form of the Orsat 1 appa- 
ratus is practically the same as that frequently used today, as 
will be seen by Fig. 15 which is a reproduction of the original cut. 
It consists of a water-jacketed gas burette terminated at its upper 
end by a branched glass capillary tube. The pipettes, in order 
from right to left, contain caustic potash, alkaline pyrogallate and 
cuprous chloride. The cock I on the branched capillary serves 
for the connection of a platinum capillary in which hydrocarbons 
mixed with air, and added hydrogen if necessary, may be burned. 
The sample of gas is brought to the burette by the water-aspira- 

1 Annales des Mines, Series 7, t.8, 485 (1875). 



APPARATUS FOR TECHNICAL GAS ANALYSIS 



63 



tor KLM which sucks a rapid stream of gas through the cock R 
and the dust filter P. The operation of the apparatus will be 
evident to anyone who has read the three preceding chapters. 

Many modifications of this burette have been prepared since 
it was first described, but the principle has not been altered. One 
group of workers has increased the complexity of the apparatus in 
an attempt to increase speed of manipulation. The most note- 
worthy change of this sort is probably the introduction of the 




Fig. 15. — Orsat apparatus. Original form. 



bubbling pipette in which, by a three-way cock on the top of each 
pipette, the gas is made to pass down a central tube and bubble up 
through the liquid of the pipette to be later drawn from the top of 
the pipette when the three-way cock is thrown to its second posi- 
tion. There are decided objections to complication in any form 
of apparatus which may receive rough treatment in transportation 
and which is frequently handled carelessly by its operators. 

The usual modifications of the Orsat apparatus possess at least 
four glass stopcocks on the various outlets of the branched tee. 



64 



GAS AND FUEL ANALYSIS 



Unless the apparatus is always manipulated by a skilled operator 
it is almost inevitable that some of the alkaline reagent from the 
pipettes will be drawn into these stopcocks. It is apparently 
equally inevitable that the cocks will as a consequence stick and 
become broken. The branched tee is itself a source of trouble 
since it is fragile and difficult to clean when stopped. In Fig. 
16 is shown a modification of the Orsat apparatus due to Allen and 

Moyer which commends itself 
for its simplicity and durability. 
The capillary glass tube is re- 
placed by one of hard rubber and 
the glass stopcocks are replaced 
by pinchcocks which are practi- 
cally as satisfactory. The pip- 
ettes themselves are of the test 
tube type and are closed at the 
top with a soft rubber stopper 
which is pressed against the 
upper shelf by the screw which 
supports the cup in which each 
pipette rests. This gives a firm 
and yet elastic support for the 
pipettes which prevents breakage 
in shipment. 

The method of operating all 
Orsat burettes is the same. The 
water of the burette should be saturated with gas similar to that 
which is to be analyzed. The gas is taken into the burette 
through the end of the capillary projecting out of the left hand 
side of the case. If the sample is drawn directly from the smoke 
flue the precautions given in Chapter I on Sampling must be 
observed. In any case the burette is filled with gas which is 
then wasted through the fourth side arm into the outside air, 
thus getting rid of the air which was in the capillary tube of the 
instrument. The sample of gas is now drawn into the burette 
and measured with the precautions given in Chapter I. In 
addition to the gas which is in the burette there is a volume of 
about 1 c.c. in the capillary tube which is entirely neglected. 
The gas is passed into the caustic pipette and C0 2 determined 




Fig. 16. — Orsat apparatus. Allen- 
Moyer modification. 



APPARATUS FOR TECHNICAL GAS ANALYSIS 65 

as described in § 1 of Chapter III, then into the second pipette 
filled with pyrogallate for oxygen (§ 4 of Chapter III), then 
into the third pipette filled with cuprous chloride for CO (§ 6 of 
Chapter III). 

This apparatus is much used for analysis of smoke gases and 
it is sufficiently accurate for this purpose. The errors which 
arise from the failure of the gas in the capillary to come into 
contact with the reagent will hardly be more than 0.1 c.c. for 
each of the gases. The tendency will be for the oxygen to be 
slightly high due to some C0 2 which did not get into the caustic 
pipette and for the CO to be high due to oxygen which did not 
get into the pyrogallate pipette. 

The Orsat apparatus is not usually employed for gases like 
illuminating gas where many constituents have to be deter- 
mined, although other absorption pipettes and even explosion 
pipettes have sometimes been made a part of the instrument. 
The errors mentioned above due to the gas remaining in the 
capillary increase with the length of the capillary and it becomes 
preferable to use the burette with detachable pipettes. 

4. Bunte's Burette. — Dr. H. Bunte 1 in 1877 described his 
burette which although in the main obsolete still has some uses 
and is illustrated in Fig. 17. It consists of a burette closed at 
the top by a three way cock a carrying a funnel tube, and at the 
bottom by a cock b. The zero of the burette is somewhat above 
the lower cock. 

A levelling bottle such as is used with the ordinary Hempel 
type of gas burette is to be connected to the lower cock. The 
sample of gas is drawn into the burette as usual and its volume 
may be read as usual. The method of reading the volume 
prescribed by Bunte is unusual. A sample of gas slightly larger 
than 100 c.c. is to be taken into the burette and the volume com- 
pressed until it reads exactly 100. Water is now poured into 
the funnel tube to the mark m etched upon it and cock a is opened 
to communicate with the funnel tube which is unstoppered. 
Some gas bubbles through the cock and the liquid above it and 
escapes into the air. The bore of the cock is so small that no 
water flows down and after the bubbling has ceased the volume 
of gas in the burette is still 100 c.c. measured under the pressure 

1 Jour, fur Gasbel, 1877, 447. 
5 



66 



GAS AND FUEL ANALYSIS 




of the atmosphere plus the column of water in the funnel tube. 
The volume of the gas is always to be read under these condi- 
tions. In order to introduce an absorbent such as NaOH into 
the burette a partial vacuum is produced by opening the lower 
cock and lowering the levelling bottle. The cock b is then 
closed, the levelling bottle disconnected and the reagent in a 
small dish is placed below the cock b so that the tip of the cock 
is immersed. On opening the cock some of the rea- 
gent will be sucked into the burette. The burette is 
then shaken to facilitate absorption, care being taken 
to hold it only by the tips so that the heat of the 
hands will not change the temperature of the gas. To 
read the volume after absorption the funnel tube on 
the top of the burette is again filled with water, and 
the upper cock opened. Water flows into the burette 
and more water is added to the funnel until with the 
upper cock still open the water remains stationary 
on the mark m. Conditions are now as they were at 
the first reading and the volume is again read. The 
diminution in volume if NaOH was the reagent, is as 
usual reported as CO2. 

Oxygen is determined by alkaline pyrogallate (§4 
of Chapter III). To avoid diluting the reagent the 
dilute caustic in the burette is sucked out as far as 
possible and 20 c.c. of the pyrogallate introduced. 
The burette is shaken at intervals for five minutes 
and then rinsed with fresh water introduced through the funnel 
tube, the pyrogallate being allowed to flow out of the lower 
stopcock. As soon as the walls of the burette are rinsed clean 
the bottom stopcock is closed and the volume read as before 
with the top stopcock open and the funnel tube filled with water. 
Carbon monoxide is absorbed by acid cuprous chloride as 
usual (§ 6 of Chapter III), but a very considerable amount of 
preliminary manipulation is necessary. The alkaline pyrogallate 
must be thoroughly washed out by water flowing through the 
burette and then replaced by HC1 sp. gr. 1.12. When this has 
been done the Cu 2 Cl 2 reagent may be added and after the 
absorption the volume measured with the funnel tube filled with 
dilute HC1. 



Fig. 17.— 
Bunte gas 
burette. 



APPARATUS FOR TECHNICAL GAS ANALYSIS 



67 



The only advantage which a burette of this type can claim is 
its portability. Its manipulation is cumbrous, the introduction 
of the large volumes of wash water changes the composition of 
the gas, and the temperature of the burette, which is usually 
not jacketed, is almost certain to change unless very unusual 
precautions are observed to keep it from contact with the 
hands of the operator and to have the temperature of the reagent 
and wash water the same as that of the room where the operation 
is being carried on. The Orsat apparatus is preferable for almost 
all purposes. 

5. Chollar Tubes.— Mr. B. E. Chollar 1 in 1888 modified 




Fig. 18. — Chollar tubes for gas analysis. 

Cooper's eudiometer and produced a very practical and simple 
combination burette and pipette. In Fig. 18 at A are seen three 
of the Chollar tubes in a rack. The zero point is the top of the 
bulb and the graduations start at the bottom of the bulb and ex- 
tend down to the bend in the tube. The bulbed portion may 
1 Proc. Western Gas Association, 1893, 219. 



68 GAS AND FUEL ANALYSIS 

occupy varying proportions of the total volume and since it is 
not graduated a tube must be chosen proportioned properly 
for the analysis to be made. Of the three burettes shown at A, 
that on the right is called a 10 per cent, burette because the 
graduations cover only 10 per cent, of the total volume. The 
middle burette is a 25 per cent, burette, and the burette on the 
left is a 50 per cent, burette, provided also with an upper stop- 
cock which is convenient, but not necessary for all the forms. 

It is assumed that a plentiful supply of gas for analysis is avail- 
able and that it is under pressure. A rubber tube is slipped into the 
burette round the bend and up to the top through which gas is 
blown until the air is displaced. It is safer to fill the tube with 
water and displace this with the gas. The rubber tube slips 
into the burette more readily if it is wet. When the burette is 
completely filled with gas it is immersed in the cylinder of water 
B far enough to seal the outlet and the rubber tube is withdrawn. 
The burette is now pressed completely under the water and kept 
there by the weighted cover C for a few minutes until the gas 
has attained the temperature of the water which should be at 
room temperature. The top of the burette is then grasped by 
the tip of the ringers to avoid warming the gas and the burette 
is raised until the meniscus inside of the burette coincides with 
the surface of the water in the glass cylinder when the gas vol- 
ume is read at atmospheric pressure. In case the volume of the 
gas has increased through expansion so that the meniscus is 
below the graduations a portion of the gas must be removed by 
closing the lower end of the burette with the thumb while it is 
still under water and then by raising and tilting the burette 
causing a few bubbles to pass into the short arm from which they 
escape into the air when the thumb is removed. 

To introduce reagents, a portion of the water is sucked from 
the short arm of the burette by a pipette as shown at D. Suf- 
ficient water must of course be left to seal the burette. Suf- 
ficient reagent such as caustic soda is then introduced to com- 
pletely fill the short arm which is tightly closed by a rubber 
stopper or the thumb. The burette is then inverted and shaken 
until absorption is believed to.be complete. The gas which may 
have gotten into the short arm is now worked back into the body 
of the burette by turning the burette almost horizontal and the 



APPARATUS FOR TECHNICAL GAS ANALYSIS 69 

burette is again immersed in the large cylinder. The rubber 
stopper is removed after the outlet is sealed with water, water 
enters to replace the gas absorbed and the volume of the gas is 
read as at first. 

The usual reagents for carbon dioxide, unsaturated hydro- 
carbons, oxygen and carbon monoxide may be used. A solution 
of arsenious oxide is recommended for hydrogen sulphide. 

To wash out one reagent before adding another the burette 
is placed on the stand shown at E in Fig. 18 with its open arm 
pointing down in a beaker of water. The reagent being heavier 
than water tends to flow out. The washing may be accelerated 
by passing water into the burette through a rubber tube. The 
instrument is very readily portable and after a little experience 
results of considerable accuracy may be rapidly obtained. 



CHAPTER VI 

EXACT GAS ANALYSIS 

1. Historical. — Lavoisier in his Traite Elementaire de Chemie 
published in 1789 devoted Chapter II of Book III to Gasometry 
or "The Measurement of Weight and Volume of Gaseous Sub- 
stances." He described eudiometers, a gasometer of the bell 
jar type, and methods of separation of certain gases by absorp- 
tion and explosion as well as the mathematical method of making 
correction for temperature and pressure. 

Bunsen and Playfair 1 in a paper "On the Gases Evolved from 
Iron Furnaces" presented in 1845 what was perhaps the first 
serious attempt to develop methods of gas analysis for technical 
investigation. The methods published in this paper formed the 
basis of Bunsen's classic book " Gasometrische Methoden" 
published in 1857. Bunsen used a graduated cylindrical eudi- 
ometer inverted over a trough of mercury both for measuring 
the volume of the gas and for carrying out analysis by absorp- 
tion and explosion. It was necessary to determine the tempera- 
ture and pressure of the gas when each reading of volume was 
made and to make arithmetical corrections to bring the volume 
to standard conditions. It was possible to work accurately 
with his apparatus but it has been replaced by simpler forms 
which allow more rapid work. 

Regnault and Reiset 2 in a paper on the respiration of animals 
developed a eudiometer which was capable of accurate work 
but was very cumbrous. 

Doyere in 1848 3 exhibited before the French Academy of 
Sciences apparatus for gas exact analysis and two years later 4 
presented details of the remarkably complete and ingenious 
apparatus which he had devised. He used a separate pipette 

1 British Ass. for Advancement of Science, 1845, 142. 

2 Ann. de Chim. et de Phys. (3), 26, 299 (1849). 

3 Comptes rendus de V Academic de -Science, Feb., 1848. 

4 Annales de Chimie, 3 Series, 28, 5, (1850). 

70 



EXACT GAS ANALYSIS 71 

for each reagent, measured his gases saturated with moisture 
instead of dry, and by means of a mechanical compensator 
avoided all corrections for change in gas volume due to tempera- 
ture and pressure. He absorbed carbon dioxide by caustic 
potash and estimated oxygen by explosion or by absorption with 
ammoniacal cuprous chloride, two pipettes being used in series 
followed by a third containing dilute sulphuric acid. He also 
studied the estimation of hydrogen by explosion. 

W. Hempel in the second edition of his Gas Analysis (1889) 
described a modification of Doyere's method in which he measured 
the gas volume in a bulb, varying the pressure of the gas at each 
reading so that its volume always filled the bulb to a definite 
mark. The pressure under which the gas stood was then meas- 
ured and correction mathematically made to find the volume 
under standard conditions. 

2. General Methods. — These earlier processes with their 
complications were necessitated by the imperfections of apparatus, 
especially stopcocks which could not be relied on to be gas- 
tight. With the development of reliable stopcocks came the 
development of apparatus so that now there is little need to use 
any of these older processes. The methods of exact gas analysis 
are now in general the same as those employed in technical 
analysis but with greater attention paid to the elimination of 
minor errors. The gas burette is graduated more accurately 
and an attempt is made to read to hundredths of a cubic centi- 
meter instead of tenths. Correction is made either arithmetically 
or mechanically for variations in temperature and pressure of 
the gas during analysis. Mercury is used instead of water as 
the confining liquid in the burette and errors due to diffusion 
in the pipette are prevented. Special methods are sometimes 
introduced for the estimation of minute constituents of the 
gas. 

3. Corrections for Temperature and Pressure. — According 
to the law of Boyle the volume of any gas varies inversely as the 
pressure and according to the law of Gay Lussac all gases expand 
under constant pressure by the same amount — about 1/273 of 
their volume — when heated from 0° C. to 1° C, and the same for 
each succeeding degree. The volume of a gas is almost univer- 
sally expressed in scientific work as that which it would occupy 



72 GAS AND FUEL ANALYSIS 

if completely dry and at a temperature of 0° C, and a pressure 
of 760 mm. of mercury. For technical purposes the gas is fre- 
quently calculated to the volume which it would have at 60° F. 
and 30 in. of mercury pressure when saturated with water. The 
formulae for this calculation are given in § 4 of Chapter VII on 
the Heating Value of Gas. 

The formula for the reduction of the volume of a dry gas to 
0° and 760 mm. dry follows from the laws stated. 

V p Tr Vp 



Vo = - - y or V 

; )760 



_M— (l-.00367t)760 

273; 



If the gas as measured was saturated with moisture at say 
60° F. and it should actually be chilled to 0° C. most but not all 
of the water would be condensed. It is usual in calculations 
to assume either that the gas becomes completely dried which 
is the usual assumption or that the water all remains in the 
vapor state which is less frequently assumed. The formula 
given above will be the one used in the latter case where the 
water vapor is assumed to obey the gas laws without condensing, 
just as nitrogen or hydrogen would. 

If the gas is to be reduced to standard conditions, dry, the 
volume of the water vapor must be deducted. Since the 
assumption is that the gas is saturated with moisture at the 
temperature "t" the proportion of moisture will be a constant 
which may be expressed either in terms of volume or more 
conveniently in terms of barometric pressure. Table I in the 
Appendix gives the vapor pressure of water, "a," for each 1° C. 
within the limits usually required. The formula for reduction 
of the volume of a gas read when saturated with moisture, to 
its volume when dry at 0° C. and 760 mm. is therefore as follows: 

_ V(p- a) 

(l-.00367t)760 

If the readings are in the Fahrenheit scale and in inches of 
barometric pressure the formula becomes 

V(p-a) 



V 



32 



('-'-£») 



EXACT GAS ANALYSIS 



73 





4. Description of Gas Burettes. — The burette for technical 
analysis does not allow an accuracy greater than 0.1 c.c. and the 
probable error is more nearly 0.2 c.c. The errors are in part 
due to the coarse graduations of the cylindrical burette tube 
and in part to liability to change in the temperature and pressure 
under which the gas volume is read. A device for automatically 
correcting for change in tempera- 
ture and barometric pressure was 
devised by Petterson 1 in an ap- 
paratus for the analysis of air. 
This was quickly adapted by 
Hempel to his gas burette and 
as used by him consisted of a 
closed tube connected to one arm 
of a manometer whose other end 
connected with one tip of a three- 
way cock at the top of the bur- 
ette. The volume of the gas 
instead of being read at a change- 
able atmospheric pressure was to 
be read at the unchanging pres- 
sure in the closed compensating 
tube. The modification of this 
type of apparatus developed by 
the author 2 is shown in Fig. 19. 

The burette has a specially 
bored stopcock as shown in the 
sketch which allows communica- 
tion to be established through the 
stopcock between the burette and 
the compensating tube. The 

latter consists of a U tube manometer shown in A of Fig. 19 
connected to the burette by a single rubber connection at a, 
placed so that gas never comes in contact with the rubber and 
there can be no possibility of leakage — a fault of the Hempel type 
of apparatus. The other end of the U tube bends down and 
terminates in a tube about the same diameter as the burette and 

^Zeit. anal. Chem., 25,467 (1886). 

2 Jour. Am. Chem. Soc, 22, 343 (1900). 








Fig. 19. — Details of gas burette 
with automatic compensator for 
temperature and pressure. 



74 GAS AND FUEL ANALYSIS 

sealed at the bottom. At the top of the U is a capillary tip which 
in practice is fused shut as explained later. 

In mounting the burette which is assumed to be clean and 
entirely taken apart the manometer is connected to the burette 
at a by a piece of good black rubber tubing wired in place, and 
the large rubber stopper at the lower end of the burette is pushed 
up until it rests snugly against the bottom of the comparison 
tube and presses the glass parts at a firmly together within the 
rubber tube. The glass water jacket tube is then slipped over 
the top of the burette and onto the lower rubber stopper and the 
upper split cork fitted into place. The burette is then placed 
in a stand such as is shown in Fig. 21. The levelling bottle is also 
connected to the burette as in technical analysis with the added 
precaution of wiring the rubber stopper into the burette so that it 
may not be blown out through the weight of the mercury column. 
The process of wiring in a rubber stopper is simple but since begin- 
ners are sometimes at a loss to accomplish it the following descrip- 
tion is given. A piece of rubber tubing is first slipped over the 
bottom of the burette to give a soft surface for the wire to grip. 
A piece of copper wire about 18 gage is annealed by passing 
several times through the flame of a Bunsen burner and a piece 
about 4 in. long is twisted in the middle of one about 8 in. long 
to form a T. The longer piece is then bent around the burette 
and twisted till it fits snugly. Its two ends are now brought 
over the rubber stopper and twisted with the free end of the 4-in. 
piece of wire until the cork is firmly pressed in. 

To prepare the comparison tube for use, a few drops of water 
are to be brought into its lower portion to saturate the air it 
contains, the manometer is to be filled with mercury and the 
capillary tip is to be fused shut. The two first operations can 
be conveniently accomplished in one operation. The burette 
is filled with mercury on whose surface are a few drops of water. 
By turning the stopcock to the position shown at D of Fig. 19, 
the water with the mercury following it may be passed through 
the stopcock and the U tube and over into the comparison tube. 
The progress of the mercury is to be arrested when the water 
has trickled down the comparison tube and the mercury is to be 
drawn back until there is just enough left in the U tube to fill it 
approximately to the calibration mark when there is atmospheric 



EXACT GAS ANALYSIS 75 

pressure on both limbs of the U as shown in Fig. 19 at A. This 
may be readily accomplished after one or two trials. The cap- 
illary tip of the comparison tube is now to be sealed with a blow 
pipe and the burette is ready for use. 

This burette has the advantage over the usual technical type 
that its readings are unaffected by variations in external tempera- 
ture and pressure, but the volumes themselves cannot be read 
more accurately than with the technical type unless a reading 
telescope is employed. Even with this aid to the eye the results 
are not always certain for the presence of a few drops of water on 
the mercury alters the shape and boundaries of the meniscus. 

5. The Bulbed Gas Burette for Exact Analysis. — The idea of 
converting the burette into a string of bulbs connected to a side 
arm burette apparently originated with Bleier. 1 

The author has utilized this suggestion in the design of the 
burette shown schematically in Fig. 20, and in perspective in 
Fig. 21; it consists of a burette with stopcock and manometer 
as already described. The main body of the burette contains 
twelve bulbs, each of a capacity approximating 12 c.c. A line is 
etched on each constriction and the capacity of the bulb between 
these marks is determined. Starting from the capillary above 
the top bulb a side arm springs, terminating in a small burette 
with total capacity of 15 c.c. and graduated in 0.1 c.c. Both 
these burette tubes connect at the bottom by means of heavy 
rubber tubes and a Y with a stopcock on each arm, to a common 
levelling bottle. A screw clamp on each rubber tube serves for 
the exact adjustment of the mercury. To measure a gas, the 
stopcock is placed in position shown at C of Fig. 19 and the 
mercury in the bulbed tube brought to the mark in one of the 
constricted portions by opening the proper stopcock on the Y 
and raising or lowering the levelling bottle. When adjusted, 
the mercury is held in its proper position by closing the stopcock 
on the Y. The stopcock leading to the small -burette tube is 
then opened and the gas brought to approximately atmospheric 
pressure by proper change in the mercury level. The three-way 
stopcock at the top of the burette tube being now turned to 
position shown at D in Fig. 19, the burette is brought into 
connection with the manometer, which is properly set by further 

iBer. d. Chem. Ges., 31, 1, 238. 



76 



GAS AND FUEL ANALYSIS 



changing the level of the mercury in the small burette. The 
final adjustment in both burettes is made by the screw clamps 
on the rubber tubes. 

When the gas burette is used in the manner indicated the gas 
volume is read under conditions which are constant but not 
necessarily known. It is not usually necessary in gas analysis 




Rubber 
Connection 




Fig. 20.— Details of 
bulbed gas burette for 
exact gas analysis. 




Burette for exact gas analysis. 



to know the absolute value of a gas but it may be obtained if the 
temperature and barometric pressure are noted at the time the 
tip of the manometer tube is sealed. The volume of the gas is to 
be read when the level of the mercury in the two arms of the man- 
ometer is the same. The gas has then the same volume which it 
would have had at the temperature and pressure prevailing 
when the manometer was sealed. Correction to standard con- 



EXACT GAS ANALYSIS 77 

ditions may be made mathematically as indicated in a preced- 
ing paragraph. This procedure for reading the gas volume is 
not as accurate as the one recommended for gas analysis where 
the mercury is brought tangent to the rim of a metal sleeve but 
it is amply accurate for most purposes. 

6. Manipulation of Gas Burette for Exact Analysis. — It is 
necessary to discharge from the burette all of the residual gas in- 
cluding that in the manometer tube. This may be accomplished 
by discharging most of the gas from the burette into the air 
and then by turning the stopcock and lowering the levelling 
bottle, drawing into the burette the gas from the manometer 
until the mercury of the U tube is just at the stopcock. The 
gas in the burette may then be discharged into the air. If there 
is danger that alkali has been introduced into the burette in a 
previous operation it is advisable to draw into the burette a few 
cubic centimeters of acidulated water and with it rinse down the 
walls of the entire burette, subsequently expelling it. This also 
makes certain that the walls of the burette are wet so that the 
gas to be subsequently introduced will become saturated with 
water. 

The gas is then introduced into the burette as in technical 
analysis. If a volume of approximately one hundred cubic 
centimeters are wanted, nine bulbs are rilled with gas at atmos- 
pheric pressure. The stopcock at the top of the burette is then 
closed and the gas compressed into eight bulbs. Up to this 
time the side arm of the burette has remained filled with mercury. 
The stopcock on the Y is now opened and part of the gas trans- 
ferred to the side arm until the whole is again under atmospheric 
pressure as shown by the agreement of the level of the mercury 
in the levelling bottle held in the hand of the operator, with the 
level of the mercury in the side arm. The stopcock on the Y is 
now to be closed and that at the top of the burette is to be turned 
to make communication with the manometer the mercury in 
which drops at once to approximately its proper position. By 
using the clamps on the rubber tubes as fine adjustments the 
meniscus in the bulbed tube is to be brought tangent to the 
mark between two bulbs and also the meniscus in the manometer 
is to be made tangent to the metal sleeve. 

The volume of the gas will be read as x c.c. in the bulbs + y 



78 GAS AND FUEL ANALYSIS 

c.c. in side burette + z c.c. in manometer. As there are these 
three readings to be made it is necessary that each be very 
accurate. Let us see how accurately this may be done. First, 
the mercury in the bulbed tube is to be brought to a specified 
mark in a tube of about 5 mm. internal diameter. By means 
of the screw clamp this may be done with such accuracy that the 
error is negligible. Second, the volume of gas in the side tube 
must be read. Each 0.1 c.c. in this tube occupies a space of a 
little over 2.5 mm. and it is possible to interpolate 0.01 c.c. with 
the eye with an error of less than 0.02 c.c. Third, the mercury 
in the manometer must be brought to a definite mark with such 
exactness that the barometric pressure, under which the gas 
volume is read, shall be almost identical each time. A difference 
of 1 mm. of mercury pressure changes the gas volume 0.13 per 
cent., which on a volume of 100 c.c. equals 0.13 c.c, an error far 
too large. It was found impracticable to attain the required 
accuracy when it was attempted to bring the mercury to a mark 
etched on the glass. The best device was found to be a band of 
thin, blackened copper, wrapped around the tube and cemented 
to the glass. It is possible to bring the mercury tangent to the 
lower surface of this with great exactness. In working with 
this burette the author is accustomed to make all readings in 
duplicate, readjusting at all points each time, and to repeat if 
the two differ from each other by more than 0.01 c.c. Dupli- 
cates usually agree within this limit. The greatest difficulty 
found in manipulation is to draw the liquid from the pipette over 
exactly to the burette stopcock and stop it there. If it gets into 
the burette, a bubble lodging in one of the capillary tubes fre- 
quently damps the sensitiveness of the manometer. If this 
happens the bubble may be shot out of its lodging place by com- 
pressing the rubber tube above the screw clamp with the fingers. 
Such a bubble may also be carried into the manometer, where 
it will obscure the surface of the meniscus. To remedy this it 
is well to keep 2 or 3 mm. of water on the surface of the mercury 
in the manometer. This allows a perfectly sharp reading of the 
mercury meniscus below the water-level. The manometer 
should respond to a very slight movement of the screw clamp. 
The advantages of this burette may be summarized as follows : 
It is a compact burette which, without reading-telescope or other 



EXACT GAS ANALYSIS 79 

accessories, allows the volume to be read with an error of less 
than 0.02 c.c, compensates automatically for changes of tempera- 
ture and pressure, and avoids completely all errors due to in- 
clusion of air or loss of gas in making connections with the absorp- 
tion pipettes. The disadvantages so far developed are chiefly 
those inherent in all forms of apparatus which possess a stopcock 
and rubber connections. Both may leak; but on the other hand 
both may be kept so tight for limited periods of time as to in- 
troduce no measurable error. 

7. Calibration of Burette. — The burette must be carefully 
calibrated throughout its entire length. This can best be done by 
weighing the mercury discharged. One cubic centimeter of mer- 
cury at 0° C. weighs 13.59 grm. Since all that is desired is a 
relative calibration the mercury need not be strictly pure nor 
need correction be made for its temperature. Ten milligrams 
of mercury corresponds to less than one-thousandth of a cubic 
centimeter so greater accuracy than this in weighing is a waste of 
time. Wire a stopper carrying a stopcock into the bulbed tube 
and fasten by a stiff rubber tube a stopcock to the side arm. It 
is especially important that the rubber tubing should not bulge 
under the mercury pressure and to prevent this it should be firmly 
wound with wire. Connect the tips of these stopcocks to the 
mercury levelling bottle and through them fill the burette with 
mercury completely to the stopcock. The portion first calibrated 
is the capillary tube from the bottom of the stopcock to the zero 
of the bulbed tube and the zero of the side arm. After that each 
bulb and each cubic centimeter of the side arm is separately 
calibrated. The accuracy of the calibration may be checked by 
the procedure of a regular analysis where a volume of gas is chosen 
such that it for instance fills 9 bulbs and a small portion of the side 
arm. The method of reading may then be changed to eight bulbs 
plus a considerable volume in the side arm but if the calibration is 
correct the same volume should, of course, be shown. The vol- 
ume of the small portion of the manometer tube above the mer- 
cury may best be determined by filling the burette completely 
with mercury and then drawing the air out of the manometer 
tube into the side arm of the burette where it may be measured 
under atmospheric pressure with an error of a few tenths of a per 



80 GAS AND FUEL ANALYSIS 

cent. Since the total volume is only a small fraction of a cubic 
centimeter the method is amply accurate. 

8. Absorption Methods in Exact Gas Analysis — The same 
reagents may in general be used in exact as in technical analysis. 
Care should however be taken to see that the reagent has been 
recently saturated with gas of a sort similar to that which is to be 
analyzed. In case the reagent is one which does not attack mer- 
cury the pipette is to be filled with mercury which carries on its 
surface only a few cubic centimeters of the reagent. If pipettes 
of the ordinary type are filled with mercury the mercury rising 
in the second bulb places the gas under considerable pressure and 
greatly increases the danger of leakage at the rubber connections. 
An explosion pipette may with advantage be used as an absorption 
pipette under these circumstances since its stopcock and levelling 
bottle allow a regulation of the pressure within the pipette. 
Where the greatest accuracy is not required it is sufficient to lessen 
the errors due to diffusion by introducing a few cubic centimeters 
of mercury to form a seal in the ordinary form of pipette. In 
the case of solutions like cuprous chloride where mercury cannot 
be used reliance must be placed on the complete saturation of the 
reagent. Where gases are readily soluble errors due to diffusion 
mount up rapidly. For instance : A sample of 74 c.c. of acetylene 
gas. when passed into an ordinary KOH pipette as used in tech- 
nical gas analysis decreased to 63.9 after quietly standing for three 
minutes, to 58.0 after a second contact, and to 29.0 c.c. after three 
minutes shaking with the same reagent. After two more similar 
periods the residue left in the burette was only 5.2 c.c. A second 
sample of gas behaved similarly, and by connecting a burette 
with the second bulb of the pipette the acetylene diffusing through 
was recovered quantitatively. 

9. Carbon Dioxide. — Carbon dioxide is usually estimated by 
absorption in caustic soda as in technical analysis. If other 
acid gases such as H 2 S, S0 2 , or HC1 are present they may be re- 
moved by first shaking the gas in a pipette containing KMn0 4 
very faintly acidified with H 2 S0 4 . An increase in volume 
after this operation would indicate that oxygen had been 
evolved during the process. . If direct evidence of the presence of 
C0 2 is desired a clear solution of Ba(OH) 2 should be used instead 
of NaOH in the pipette for C0 2 absorption. The formation of a 



EXACT GAS ANALYSIS 81 

white precipitate completely soluble in HC1 will show the presence 
of carbonates. 

10. Unsaturated Hydrocarbons. — Unsaturated hydrocarbons 
as a class are estimated as in technical gas analysis by absorption 
with fuming sulphuric acid or bromine water. It is difficult to 
prevent the errors due to diffusion mentioned in § 8 since both 
reagents attack mercury. Where it is desirable to eliminate the 
error as far as possible a stopcock may be placed in the line be- 
tween the two bulbs of the pipette which can be closed after the 
gas has been passed into the pipette while absorption is taking place. 

A separation of the constituent unsaturated hydrocarbons is 
rarely carried out. It is best accomplished by bubbling a known 
volume of the gas through bromine and fractionating the resulting 
bromides. The results are at best unsatisfactory. Ernshaw 1 
has shown that it is possible to calculate the average composition 
of the illuminants from data obtained by exploding a sample of 
the gas which still contains the olefines and deducting from the 
observed contraction and carbon dioxide the amounts due to 
hydrogen, carbon monoxide and the paraffines. The method de- 
mands very accurate work. 

Acetylene may be absorbed in a faintly ammoniacal solution of 
silver or copper salts. The precipitated acetylides are explosive 
when dried and care should be taken in handling them. The 
ammonia vapors are to be removed from the gas by shaking with 
dilute acid before the volume is measured. Water dissolves more 
than its own volume of acetylene, so great care must be exercised 
to saturate the water of containing vessels before the gas to be 
analyzed is brought into them. Also gas from which large per- 
centages of acetylene have been removed must not be returned to 
vessels containing much water with which it had previously been 
in equilibrium since the water will give back to the gas material 
amounts of acetylene. 

Phosphorus forms a delicate reagent for qualitative detection 
of traces of unsaturated hydrocarbons. If when the gas in 
question is brought in contact with phosphorus under the con- 
ditions prescribed for the estimation of oxygen, white fumes 
form, it is certain evidence of the absence of more than minute 
traces of unsaturated hydrocarbons. If on the other hand the 

1 Jour. Franklin Inst., 146, 161 (1898). 



82 GAS AND FUEL ANALYSIS 

fumes fail to appear even after the addition of air it is not 
absolutely certain that the inhibiting catalyzer is an unsaturated 
hydrocarbon for ether, chloroform and a number of other sub- 
stances behave similarly. 

11. Oxygen. — The estimation of oxygen by phosphorus as 
in technical analysis admits of little improvement in simplicity 
or accuracy. Alkaline pyrogallate may be used where it is not 
possible to remove the inhibiting catalyzers which prevent the 
use of phosphorus. 

12. Carbon Monoxide. — It was stated in Chapter II that 
the methods for estimation of carbon monoxide were unsatis- 
factory. They are more unsatisfactory for exact than for 
technical analysis. The absorption by cuprous chloride given 
in technical methods is hardly to be considered as an accurate 
method. The change in the absorption spectrum of blood after 
treatment with carbon monoxide may be made an accurate 
qualitative test for carbon monoxide but does not lend itself 
readily to quantitative purposes. 

The method usually employed is to oxidize the carbon monoxide, 
after having made certain that all other compounds which 
would be affected by the oxidizing agent have been removed. 

Iodine pentoxide is the most commonly employed oxidizing 
agent, the reaction being: 

I 2 5 +5CO = I 2 +5C0 2 

The especial value of this reaction lies in the ease with which 
the iodine formed may be estimated, it being the iodine and not 
the carbon dioxide which is used to measure the amount of 
carbon monoxide. The details here given are essentially those 
of Kinnicutt and Sanford, 1 who used substantially the method 
of Nicloux. The gas is first purified by being bubbled slowly 
through concentrated sulphuric acid and then passed through a 
tube containing lumps of caustic soda. This treatment removes 
unsaturated hydrocarbons, hydrogen sulphide, sulphur dioxide 
and similar reducing gases. The purified gas is then passed 
through iodine pentoxide contained in a U tube immersed in an 
oil bath at 150° C. Following the U tube comes another ab- 
sorption tube containing about 0.5 g potassium iodide dissolved 
1 Jour. Am. Chem. Soc, 22, 15 (1900). 



EXACT GAS ANALYSIS 83 

in 10 c.c. of water. If a liter of gas is used as small an amount 
as 0.025 c.c. of carbon monoxide may be detected. The method 
is ordinarily only used for the detection of minute amounts of 
carbon monoxide and it is not suitable for large amounts. 
The absence of any liberated iodine may be considered a positive 
proof of the absence of carbon monoxide. The liberation of 
iodine is however only a proof that some reducing substance 
was present, which can only with certainty be claimed as carbon 
monoxide after careful blank tests have shown that the purifying 
train is adequate to remove all other reducing substances and 
that the iodine pentoxide does not yield iodine except in the 
presence of such a reducing substance. 

Gill and Bartlett 1 tested this method on illuminating gas 
and report results about nine per cent. high. They report 
accurate results when mixtures of carbon monoxide and air are 
used. 

13. Hydrogen. — Hydrogen may be directly absorbed in 
metallic palladium but is almost always oxidized. The gas 
should first be freed from unsaturated hydrocarbons and other 
reducing gases as well as oxygen, so that it contains only hydrogen, 
saturated hydrocarbons and nitrogen. There is then a choice 
of methods — one class oxidizing the hydrogen without affecting 
the hydrocarbons, and the other simultaneously oxidizing both 
hydrogen and hydrocarbons. 

There are several methods for fractional oxidation of hydrogen 
which are reliable. The errors which attend the method of 
simultaneous oxidation of hydrogen and methane have been 
briefly discussed in Chapter IV. The important systematic 
error in explosions and flame combustions is due to the oxidation 
of nitrogen. The formation of oxides of nitrogen increases with 
higher temperatures. The most favorable mixture for their 
formation is one in which there are equal volumes of oxygen and 
nitrogen. The errors are therefore minimised by keeping the 
temperature of combustion low and by making the diluting gas 
as nearly pure oxygen as possible. It is not possible to give an 
absolute statement of the magnitude of the error introduced 
for it will vary with each difference in the form of the explosion 
vessel and in the violence of the explosion. The following 

1 Jour. Ind. and Eng. Chem., 2, 9 (1910). 



84 



GAS AND FUEL ANALYSIS 



series of measurements by the author 1 will indicate the magnitude 
of the error and also the accuracy of the burette for exact gas 
analysis described in this chapter. 

EXPLOSION OF PURE HYDROGEN 



Hydrogen, 
c.c. 


Air, 
c.c. 


Contraction 
after explo- 
sion, c.c. 


Calculated 
per cent, 
hydrogen 


Contraction 
over potas- 
sium hydrox- 
ide, c.c. 


Explo- 
sive 
ratio 


11.35 


84.80 


16.90 


99.26 


0.00 


4.64 


12.11 


85.57 


18.08 


99.53 


0.00 


4.37 


14.19 


84.27 


21.27 


99.92 


0.00 


3.62 


16.77 


85.77 


25.13 


99.90 


0.01 


3.06 


16.54 


82.64 


24.76 


99.80 


0.01 


3.00 


18.19 


83.22 


27.29 


100.01 


0.01 


2.71 


21.10 


83.28 


31.74 


100.28 


0.00 


2.29 


27.04 


83.86 


40.80 


100.59 


0.11 


1.73 



The hydrogen was prepared by the action of caustic potash 
on aluminium so as to be free from hydrocarbons. It will be 
noted that in this series air was used to supply the oxygen and as 
the diluent. A variation of 1.3 per cent, in the purity of hy- 
drogen due solely to errors inherent in the explosion process make 
it evident that the method can hardly be called an accurate one. 

The errors attendant upon the flame combustion method of 
Dennis and Hopkins described in § 9 of Chapter IV are illustrated 
in the following series. 

COMPARISON OF EXPLOSION AND COMBUSTION METHODS 

ON HYDROGEN 

Explosions with Air 



Sample 

hydrogen 

c.c. 


Air 
c.c. 


Contraction 
after explo- 
sion, c.c. 


Contraction 
over potassium 
hydroxide, c.c. 


Hydrogen 
per cent. 


Explo- 
sive 
ratio 


15.32 
18.15 


85.34 
82.39 


22.71 
26.93 


0.04 
0.06 


98.82 
98.91 


3.43 
2.73 



Explosions with Oxygen 



Oxygen 



14.82 


93.51 


22.04 


0.02 


99.14 


3.91 


16.48 


82.18 


24.51 . 


0.02 


99.15 


3.02 


20.58 


80.09 


30.60 


0.03 


99.12 


2.29 



^Jour. Am. Chem. Soc, 23, 476 (1901). 



EXACT GAS ANALYSIS 



85 



Combustions by the Dennis and Hopkins Method 



Hydrogen 
c.c. 


Oxygen 
c.c. 


Air 
c.c. 


91.29 

58.48 
89.31 


51.65 
53.39 

40.77 


54.55 
50.14 
50.21 



Contraction 
after explo- 
sion, c.c. 



Contraction 


Hydro- 


over potassium 


gen 


hydroxide, c.c. 


per cent. 


0.04 


99.84 


0.10 


99.66 


0.07 


99.70 



Oxygen 
in excess 



136.72 

87.43 
133.57 



13.72 

40.89 

3.73 



The values obtained by explosion with oxygen are remarkably 
concordant and are probably as accurate as we can hope to 
attain. The values obtained by explosion with air are higher 
and more irregular. The values of the Dennis and Hopkins 
method are also high and involve an error of about 0.6 per cent. 

14. Methane. — There are no absorption methods for methane 
which are acceptable. It is estimated by oxidation to C0 2 
and H 2 with measurement of the change in volume after 
oxidation and after absorption of the C0 2 . The general methods 
are given in § 7 to 1 1 of Chapter IV. There is greater liability of 
error in the explosion process through formation of oxides of 
nitrogen than is the case with hydrogen, as is illustrated by the 
following series of tests of methane made from methyl iodide 
and the zinc copper couple. 

EXPLOSION OF METHANE 



Sample 

methane 

c.c. 



Air 
c.c. 



Contrac- 
tion after 
explosion 



Carbon 

dioxide 

c.c. 


Methane 
per cent. 


Hydro- 
gen per 
cent. 


Explo- 
sive 
ratio 


6.53 

8.31 
8.54 
9.63 


92.62 
93.28 
94.15 
94.41 


0.28 
0.14 
0.14 
0.06 


4.05 
3.53 
3.19 
2.61 



Ratio 
contrac- 
tion 
sample 



7.05 

8.93 

9.07 

10.20 



92.07 

104.17 

98.35 

98.22 



13.09 
16.66 
17.10 
19.27 



1.85 

1.86 
1.88 
1.89 



In these experiments the explosive ratios all lie within the limits 
set by Bunsen. Still there is a variation of 1,6 per cent, in the 
apparent percentage of methane as calculated by the usual 
methods and a corresponding variation in the amount of hydro- 
gen. Similar experiments made with commercial oxygen (96.5 
per cent, pure) as the diluting agent instead of air showed errors 
rather greater than when using air in similar amount. The 
greater error in analyzing methane as compared with hydrogen 



86 GAS AND FUEL ANALYSIS 

results almost certainly from the higher temperatures attained 
in the explosion of methane. It is not possible to dilute the gas 
sufficiently to avoid this danger without running the risk of 
incomplete combustion of the methane. The methods of 
oxidation of methane which involve flame as in explosion or the 
Dennis and Hopkins method cannot be considered very accurate. 
Jaeger's method of analysis by combustion with copper oxide 
in a combustion tube as described in § 11 of Chapter IV 
cannot involve the formation of material amounts of oxides 
of nitrogen. This method is not so rapid or convenient as 
the others but, if care is taken to carefully cool the gas includ- 
ing that remaining in the combustion tube to its initial temper- 
ature before noting the change in volume, it is believed to be the 
most accurate method. 

15. Nitrogen. — The method of removal of all gases except 
nitrogen by combustion with copper oxide as given in § 12 of 
Chapter IV is fairly exact. The gases of the argon group are 
left with the nitrogen but the separation of these is not included 
in this work. 



CHAPTER VII 
HEATING VALUE OF GAS 

1. Introduction. — The heating value of gases may be deter- 
mined by combustion in a bomb calorimeter but the difficulty 
of transferring a definite quantity of gas to the bomb prevents 
the general adoption of such a method. The standard type of 
calorimeter is one in which the gas is burned with atmospheric 
air and the total heat of the products of combustion is as com- 
pletely as possible transferred to the water of the calorimeter. A 
continuous flow calorimeter is usually employed wherever a 
sufficient amount of gas is available, but the intermittent type is 
also used. In some other types of calorimeter the heat of com- 
bustion is used to raise the temperature of a piece of metal, or a 
thermocouple placed in the name. Calorimeters of these latter 
types give merely relative figures which can only be converted 
into heat values after very careful calibration. They are in 
no sense standard instruments and are not discussed in this book. 
It is also possible to calculate the heating value of the gas from 
its chemical composition with approximate accuracy. 

2. Continuous Flow Calorimeters. — The continuous flow 
calorimeter bears much resemblance to the type of instantaneous 
water heaters found in bath rooms. The gas after passing 
through a meter, is burned in a Bunsen burner. The products of 
combustion give up their heat to a stream of cold water flowing in 
a direction opposite to that of the gases so that the gases emerge 
from the instrument cold and the water emerges hot. 

The process to be accurate requires the fulfillment of the follow- 
ing conditions: 

a. The gases must be accurately measured, be burned at a 
constant rate, and combustion must be complete. 

b. The water must enter at a constant rate and at constant 
temperature, and be at approximately room temperature. 

c. The heat of combustion must all be transmitted to the 

87 



88 GAS AND FUEL ANALYSIS 

water whose mass and rise in temperature must be accurately 
determined. 

The pioneer calorimeter of this type was that devised by Hugo 
Junkers in 1893. 1 It is an excellent and widely used instru- 
ment which has in recent years had several imitators. It 
will be described in detail after a discussion of the general 
principles. 

3. Wet Gas Meters. — The gas is usually measured in a wet 
meter which consists of a horizontal cylindrical casing of sheet 
metal enclosing a horizontal drum and filled about half full of 
water. The drum is divided with slant partitions into three or 
four compartments, each with its own entrance for gas at the 
back and its exit at the front. Each of these compartments con- 
stitutes a distorted screw thread enlarged to a chamber in the 
center. As the inlet of one of these compartments comes out of 
the water the pressure of the gas entering causes the drum to 
revolve and the compartment fills with gas. When the compart- 
ment is full the inlet dips below the water and seals, the outlet 
unseals and the water entering the compartment drives out the 
gas before it. If there were only one or two compartments the 
flow of gas could not be continuous, but with three or four com- 
partments in the drum, one is always discharging and the rate of 
flow of gas is about constant. 

It will readily be seen that the capacity of each compartment 
and the time of sealing and unsealing the inlet and outlet will 
be affected by the height of water in the meter so that the exact 
setting of the water level becomes of great importance. Each 
meter is provided with a gage glass and a pointer which can be 
adjusted to indicate the proper water level. The Committee on 
Calorimetry of the American Gas Institute in its 1912 report 
states that even with careful work an error of 0.3 per cent, may 
be introduced by inaccurate adjustment of the water level and 
that on passing 100 cubic feet of gas through the meter an error of 
about equal magnitude may be introduced through evaporation 
of the water. The meter must be calibrated frequently for accu- 
rate work. 

Although it may be desirable to use the imported Junkers 
calorimeter, there is no similar reason for using the German meter 

1 Jour, fur Gasbel., 36, 81 (1893). 



HEATING VALUE OF GAS 



89 



which reads in the metric system. An American meter passing 
0.1 cu. ft. per revolution is much more convenient. 

The gas meter must be calibrated by passing through it a 
known volume of gas. This known volume may most accurately 
be obtained by the use of what is known as a cubic foot bottle or a 
smaller container of the same type. Containers of this type 
should be rigidly made of glass or metal and tapered at the top and 
bottom to glass tubes of small diameter upon which zero marks are 
etched. The capacity of one of these containers is determined by 
the weight of water which it contains. They may be bought in 
elaborate forms and with the certificate of the Bureau of Stan- 
dards. Where a standardized bottle is not available a sufficiently 
accurate substitute may be improvised from a gas holder of the 
type shown in Fig. 24. This consists of a cylinder of galvan- 
ized iron coned and terminated with a cock at both ends. If 
this is filled with water at room temperature and weighed, and 
then drained and weighed, the volume of the tank may be cal- 
culated from the following table. The volume thus obtained 
may be considered constant within ordinary ranges of temper- 
ature since the coefficient of expansion of mild steel is only 
0.0000067 per degree Fahrenheit. 

The tank shown in the illustration holds one-third of a cubic 
foot and is weighed upon the balance shown in front of it. If 
larger tanks are used they must be made of heavy material so as 
not to change in volume when filled with water. 



WEIGHT OF ONE CUBIC FOOT OF WATER 

50° F 62.41 lb. 

60° F 62.37 1b. 

70° F 62.311b. 

80° F 62.23 1b. 

90° F 62.13 1b. 



In making the test the tank is to be filled absolutely full of 
water of almost room temperature and left standing by the side 
of the meter in a room of fairly constant temperature for several 
hours to make sure that all the parts of the system are at the 
same temperature. The gas supply is to be bubbled through 
water in order to be certain that it is saturated with water vapor. 



90 GAS AND FUEL ANALYSIS 

If the depth of water in the saturator is so adjusted that no gas 
bubbles through unless a very slight suction is applied, it will 
obviate mathematical corrections, because if the static pressure 
of the water in the saturator is adjusted to counterbalance the 
pressure of the incoming gas, and the outlet of the discharge 
from the tank is set at the level of the lower cock, a direct com- 
parison of the volume of gas registered by the meter and the capac- 
ity of the tank gives the calibration factor for the meter without 
any calculation for difference in pressure. So long as the whole 
system is at the same temperature it is immaterial what the 
temperature is. The upper cock of the tank may now be con- 
nected directly to the outlet of the meter. The lower cock of the 
tank should have a rubber tube attached which drops down to 
allow the formation of a water seal and rises again to discharge the 
water at the level of the cock. If now the lower cock on the tank 
is opened water will flow out through the rubber tube and an 
equal volume of gas will flow through the meter. When the water 
is all out of the tank the gas will be automatically stopped by 
the water seal in the rubber outlet tube and the whole system 
will be under atmospheric pressure, which is a condition necessary 
for accurate work. 

4. Corrections for Temperature and Pressure. — The volume 
of the gas used in a test must be corrected for temperature and 
pressure. The standard conditions for the United States and 
Great Britain are a temperature of 60° F. and a barometric 
pressure of 30 in. of mercury. The gas as it comes from the wet 
meter is assumed to be saturated with water and correction is 
made for the excess of water vapor over that normal for 60°. 
Tables giving the correction factors in convenient form have been 
issued by the Gas Referees of London. They are derived accord- 
ing to the formula. 

1 7.64(h-a) 
n ~~ 460+t 

where n = factor sought 

h = height of barometric column in inches mercury 
a = vapor tension in inches of mercury at temp, t 
t = observed temp, of meter in degrees F. 



HEATING VALUE OF GAS 91 

Although this formula apparently involves the full correction 
for vapor tension which would reduce the volume of gas to a dry 
basis at 60° F., there is a further correction contained in the figure 
17.64 of the formula which corrects the gas to a basis of 60° F. 
when saturated with water. The full formula is as follows: 

/ —^Af, , 60-32\ /h-a\ / 30 \ 

n = 1+ t3? (1+-49T-) (-go") (30^51) 
\ 491 / 

The first member of the formula corrects the volume to 32° F., 
the second to 60° F., the third to dry gas under 30 in. barometric 
pressure, and the fourth to gas saturated with moisture at 60° 
F. the 0.51 being the vapor pressure of water at 60 ° F. Table 
III in the Appendix gives the factors for each degree Fahrenheit 
and each 0.1 in. pressure within wide limits. 

5. Control of the Water. — The water supply must always be 
sufficient to keep the overflow on the small elevated constant- 
level tank in operation. If the supply of water to the tank 
slackens much the rate of flow to the calorimeter will also change. 
The temperature of the water should also be constant and 
approximately that of the room. In order to insure a water 
supply of even temperature and pressure it is advisable to install 
in the calorimeter room an elevated tank of at least 20 gallons 
capacity connected to the water mains and provided with an over- 
flow from which the supply for the calorimeter is drawn. 

6. Measurement of Temperature. — The temperature of the 
inflowing and outgoing water is determined by thermometers 
which should read to tenths of a degree. They must be carefully 
calibrated throughout their length by comparison with a stand- 
ard. It is immaterial whether they are Centigrade or Fahrenheit 
thermometers but the Fahrenheit are more convenient, when as 
is customary, the results are to be expressed in British thermal 
units per cubic foot of gas. The thermometers are to be carefully 
placed in the calorimeter so that their bulbs are completely sur- 
rounded by water and are nowhere in contact with the metal of 
the calorimeter. 

7. Measurement of Mass of Water. — The mass of water 
heated during an experiment may be determined either by meas- 
urement or by weight. A 2000-c.c. graduated cylinder is fre- 



92 GAS AND FUEL ANALYSIS 

quently used. This is not an ideal device, for not only are the 
graduations coarse but the varying temperatures at which the 
water is measured necessitate the use of different correction 
factors to reduce the volumes to the equivalent weights. It is 
much more satisfactory to weigh the water. If the thermometers 
are in the Fahrenheit scale it is more convenient that the balance 
shall weigh in pounds and hundredths of a pound. If the ther- 
mometers read in the Centigrade scale it is more convenient to 
preserve the metric unit throughout. The water should be 
weighed in a metal bucket or glass vessel for which a counter- 
poise is provided. It is convenient to counterpoise the bucket 
with the interior wet as it is just after the water has been poured 
out after a test. Its weight will be so nearly constant that it is 
not necessary to counterpoise after each test. The balance 
should be capable of carrying ten pounds on each pan with a 
sensitiveness of one-hundredth of a pound. 

8. Junkers' Calorimeter. — The original form of Junkers' 
gas calorimeter is shown in Fig. 22 and the improved form in 
Fig. 23. The Committee on Calorimetry of the American Gas 
Institute suggested that the older type of Junkers' calorimeter 
would be improved if the inlet and outlet thermometers were 
brought to the same level so as to facilitate rapid reading of the 
two.- This change has been effected in the improved instrument 
but it is claimed by some observers that the efficiency of the 
newer type is not so high as the older. The numbers and letters 
refer to the same parts in each figure and the same description 
will answer for both of these instruments as well as for others of 
the same type put out by other manufacturers. The gas coming 
from the meter is burned in a Bunsen burner placed in the cylin- 
drical combustion chamber of the instrument. The hot gases 
rise in the central chamber, pass down through a series of small 
tubes in the annular water jacket surrounding the combustion 
chamber, unite again in a single flue at the bottom of the instru- 
ment and pass out through an orifice whose size may be regulated 
by a damper. Water enters through the rubber tube w to the 
small elevated tank a which serves to supply water to the cal- 
orimeter under a constant head. The amount of water flowing 
into the instrument is controlled by the valve b and the waste 
water from a is discharged at c. The water traversing the instru- 



HEATING VALUE OF GAS 



93 



ment passes out at d and during the actual test is measured in 
the graduated cylinder shown, or collected in a vessel and subse- 
quently weighed. 

The operation of the instrument is shown in detail in Figs. 22 
and 23. The sectional illustration shows the burner (2) prop- 





Fig. 22a. — Junkers' gas calorimeter. 
Original form. 



Fig. 22b. — Section of Junkers' 
gas calorimeter. Original form. 



erly placed in the combustion chamber (1) and the path of the 
combustion gases and the water. The products of combustion 
rise in the central chamber, turn at the top, descend the annular 
cooling chamber (3) to the drum (4) pass the thermometer (5) 
and escape at (6) . The water rises to the small overflow cup (7) 



94 



GAS AND FUEL ANALYSIS 



traversing a filter of wire gauze. The excess of water overflows 
and passes out of the instrument to the waste pipe through a 
rubber tube attached at (8). The small vessel (7) must always 
be kept overflowing to insure a constant pressure and hence a 




Fig. 23a. — Junkers' improved gas 
calorimeter. 



Fig. 23b. — Section of Junkers' im- 
proved gas calorimeter. 



constant supply of water through the valve (9). The water pass- 
es the thermometer (10) which registers the inlet temperature 
and in the newer form of instrument descends in a small pipe 
within the outer casing to the bottom of the instrument. In 
both forms of instrument the water rises in the annular chamber 



HEATING VALUE OF GAS 95 

surrounding the gas passages (3), thus passing in a direction 
opposite to that of the combustion gases. The water from the 
annular chamber passes through the drum (11) provided with 
baffle plates to mix it and insure that all parts of the stream are 
of uniform temperature, passes the thermometer (12) which 
registers the outlet temperature, to the overflow vessel (13) and 
out at (14). 

The water formed in the combustion of the hydrogen and 
hydrocarbons of the gas is condensed as it descends the annular 
condenser (3) and passes out of the drip shown at (15) and at e 
and is caught in a graduated cylinder. The working parts of the 
calorimeter thus described are insulated from the room by an 
air jacket. The outer casing of the calorimeter is nickel-plated 
and to be kept polished to lessen the loss of heat by radiation. 
It is well to drain the calorimeter when not in use by opening the 
cock (16). There is some danger that air brought in by the in- 
coming water may collect around the inlet thermometer and 
disturb the accuracy of its readings. In the improved form, 
the tube (h) shown at the top of the calorimeter in Fig. 23 is to 
allow such bubbles to escape. Any water entrained by the bub- 
bles passes out of the small overflow. 

9. Preliminaries of a Test. — The calorimeter is to be set up 
on a table where the light is good, where there are no draughts, 
and where there is a water supply and a waste pipe. Fig. 24 
shows the calorimeter set in a hood which has been modified by 
lowering a portion of the floor to bring the thermometer more 
nearly on a level with the eye of the observer. On the top of 
the hood is a zinc-lined wooden tank connected to the water 
supply and provided with an overflow pipe, from which the 
water supply for the calorimeter is drawn. This large overflow 
tank is advisable as it compensates for variations in the tempera- 
ture and pressure of the city water supply. 

The first step is to turn on the water and regulate the supply 
so that it flows through the instrument at the rate of approxi- 
mately 1.5 to 2.0 liters per minute in case illuminating gas of 
ordinary quality is to be tested. The water must continuously 
overflow from both cups (13) and (8) of Figs. 22b and 23b. 
No water should drip from spout (15) nor from any other part 
of the instrument. 



96 



GAS AND FUEL ANALYSIS 



The gas meter is to be levelled and more water added if neces- 
sary to bring the bottom of the meniscus of the water on a level 
with the pointer. This is to be done when there is no gas pressure 
on the meter, and to ensure this state of affairs the burner cock 
on the outlet of the meter should be open and an opening should 
be made to the air on the inlet side of the meter. This may 
usually be most conveniently effected by disconnecting the rub- 
ber tube, but may also be accomplished by unscrewing the small 
plug at the bottom of the well below the gas inlet. This also 




Fig. 24. — Gas calorimeter and accessories. 



serves the purpose of removing any water which may have 
spattered into the gas inlet. The probable error in adjusting 
the water level is 0.3 per cent, so that when a greater accuracy 
is required the meter should be recalibrated after adjustment. 
The gas supply is to be connected to the meter and then to the 
calorimeter. A pressure regulator should be unnecessary on a 
city gas supply if the meter works smoothly. Directions are 
frequently given to interpose a regulator of the floating bell-jar 
type between the meter and the calorimeter. If this is done 



HEATING VALUE OF GAS 97 

it must be watched closely because any variation in the heights 
of the drum of the regulator at the beginning and end of the test 
causes an error in the measurement of the gas. Long connections 
of rubber tubing are to be avoided since rubber is porous and also 
exerts a selective solvent action on the hydrocarbons of the gas. 
The connections should be of glass with short lengths of rubber 
on each end. 

The system is to be tested for leaks by closing the burner cock 
and opening the inlet cock on the gas main. The large hand of 
the meter should not show any perceptible change in position 
after two minutes. When the system has been found to be tight 
the burner cock may be opened and the gas allowed to escape 
into the air of the room until the large hand of the meter has made 
one complete revolution. It may then be lighted without danger 
of explosion unless the gas is acetylene, uncarburetted water gas 
or similar gases having wide explosive limits. Be sure that no 
unburned gas gets into the calorimeter where it might cause ex- 
plosion later. 

The flame from the burner is to be regulated so that it is a 
clear blue color with just a tinge of yellow at the tip. The 
volume will depend on the quality of the gas. Special tips for, 
gases of very high or low heating value are provided with the 
instrument. With ordinary illuminating gas the rate of flow 
should be between 5 and 7 ft. per hour. The gas should be burned 
with a small excess of air. The draft may be controlled by the 
butterfly valve (6) of Figs. 22 and 23. The valve should be set 
to give maximum readings of the thermometer on the water 
outlet. That setting which gives the highest result is the most 
accurate. The flame must burn perfectly steadily. If it flickers 
the most probable cause is the presence of water in some of the 
connections. The rubber tubing should be disconnected and 
drained, the plug in the well below the inlet of the meter removed, 
and the pressure regulator examined. It may be that the flicker- 
ing is due to friction within the meter which causes the drum to 
stick. This can usually be observed by closely watching the 
large hand of the meter and observing if it lags at particular 
points of its revolution. Trouble from this source cannot 
usually be remedied without sending the meter back to the fac- 
tory. Flickering of the flame of the test burner may also be due 



98 GAS AND FUEL ANALYSIS 

to fluctuations in the pressure of the gas in the mains or services. 
A U-gage attached to a gas outlet will show whether this is the 
case. If it is necessary to test gas under these conditions the 
flickering may be lessened by interposing between the gas outlet 
and the meter a large empty bottle. Care must be taken to fill 
this bottle completely with water and then displace this with gas 
to avoid danger of explosion. 

If the meter has been recently filled with fresh water the gas 
should be allowed to burn for an hour before the test in order that 
the water of the meter may become saturated and not cause any 
change in the composition of the gas passing through it. 

10. Description of a Test. — When the gas and water supply 
and the burner have been thus adjusted, the lighted burner may 
be placed in the calorimeter, care being taken to properly center 
it. This operation is facilitated by a small mirror placed below 
the instrument. The thermometer in the outlet water will at 
once commence to rise, and in a few minutes will be constant to 
within a few tenths of a degree. The increase in temperature of 
the outflowing over the incoming water should not be more than 
10° C. and it may be necessary to readjust the water and gas 
supply to obtain this condition. If it is necessary to change the 
adjustment of the gas the burner should be removed from the 
calorimeter. The butterfly valve must not be closed enough to 
prevent the flame from burning strongly and freely. The escap- 
ing gases should not have any odor of unburned gas. Their 
temperature should be only a few degrees above that of the water 
entering. 

The water formed in the combustion of the hydrogen and 
hydrocarbons will condense in the calorimeter and commence 
to drip from the small spout at the bottom of the instrument. 
The test should not be commenced until the thermometer on the 
water outlet has remained constant for several minutes and the 
condensed water has also commenced to drip from its spout 
showing that equilibrium has been reached within the calorimeter. 

The counterpoised bucket for the water is placed in a conve- 
nient position and as the large hand of the meter passes a zero 
mark the water is turned into the bucket. Both thermometers 
are now to be read at each quarter position of the meter hands or 
more frequently. The outlet thermometer sometimes fluctuates 



HEATING VALUE OF GAS 99 

rapidly and it is well under such circumstances to read it as many 
times as possible so as to obtain a fairer average. A consumption 
of 0.2 of a cubic foot, or two revolutions of the large meter hand is 
sufficient with illuminating gas. The last thermometer readings 
will be made when the meter hand is in the three-quarter position. 
The operator then watches the meter while holding one hand on 
the tube through which the outlet water is flowing and as the 
meter hand again reaches the zero he swings the tube out of the 
bucket, thus marking the completion of the test. After the water 
has been weighed a duplicate test may at once be started. The 
procedure is the same in case the water is to be measured in a 
graduated cylinder instead of being weighed. The volume 
readings of the cylinder must be converted into grams by means 
of the table in § 6 of Chapter XVI on Manipulation of the Bomb 
Calorimeter. It is not possible to read the volume very accu- 
rately in a wide graduated cylinder. 

The water of condensation dripping from the instrument is to 
be measured to allow the calculation of the net heating value. 
It is accurate enough to catch the water formed from 1 cu. ft. 
in a 50 c.c. graduated cylinder. 

In case the temperature readings have not stayed constant 
within a few tenths of a degree during the test, the results should 
be discarded and an attempt be made to better the conditions. 

If for any reason the burner goes out during a test and unburned 
gas gets into the instrument, it must be expelled before again 
lighting the flame. This may readily be accomplished by 
blowing vigorously through the escape pipe of the combustion 
gases. 

11. Calculation of Results. — The heating value of gas is 
usually expressed, in English speaking countries, in British 
thermal units per cubic foot of gas measured when saturated 
with moisture at 60° F. and under a barometric pressure of 30 in. 
of mercury. The method for correcting the observed volume of 
gas to these standard conditions has been described in § 3. The 
factors for converting cubic centimeters of water at various tem- 
peratures to grams are given in § 6 of Chapter XVI. A Calory 
is accurately enough defined as the amount of heat required to 
heat 1 kg. of water 1° C, and a British thermal unit to be the 
amount required to heat 1 lb. of water 1° F. irrespective of the 



100 GAS AND FUEL ANALYSIS 

absolute temperature of the water. The formula for calculation 
of the heating value is 

Hy= m(t'-t) 

V 

where m = mass of water heated 

t' = mean temperature of water flowing out 
t = mean temperature of water flowing in 
v = corrected volume of gas burned 

If m is expressed in pounds, t in degrees Fahrenheit and v 
in cubic feet, the result is at once British thermal units per cubic 
foot. 

If m is expressed in kilograms, t in degrees Centigrade and v 
in cubic feet, the result is in the hybrid unit Calories per cubic foot 
which may be corrected to British thermal units per cubic foot by 
multiplying by 3.968. 

If m is expressed in grams, t in degrees Centigrade and v in 
liters the result will be in the metric unit, small calories per liter 
which is the same as Calories per cubic meter. This is the method 
of reporting heat values in Germany and other countries which 
use the metric system. To convert Calories per meter to 
British thermal units per cubic foot of gas measured under the 
same condition multiply by .1124. In scientific work the heating 
value of a gas is usually reported as Calories per cubic meter of 
dry gas at 0° C. and 760 millimeters pressure. In technical work 
in Germany the gas volumes are usually corrected to 15° C. and 
760 mm. pressure which makes the conditions practically the 
same as prevail in this country. 

The following calculations are for a test where an American 
meter passing 0.1 cu. ft. per revolution and provided with a Fah- 
renheit thermometer was used, while the calorimeter ther- 
mometers were of the metric system and the water was weighed 
in kilograms. 

Meter reading at start 21 . 200 

Meter reading at close 21 . 400 

Meter temp 71° F. 

Barometer * 29.8 

Correction factor for temperature and pressure 0.965 

Correction factor for meter . 996 



HEATING VALUE OF GAS 101 



Temperature of water 




In 


Out 


12.1° C. 


21.5° C. 


12.1° C. 


21.5° C. 


12.2° C. 


21.5° C. 


12.2° C. 


21.6° C. 


12.2° C. 


21.7° C. 


12.2° C. 


21.7° C. 


12.1° C. 


21.6° C 


Average. 12. 16° C. 


21.60° C. 



Rise in temperature of water 9 . 44° C. 

Weight of water heated 3 . 164 Kg. 

Temp, of waste gases 66° F. 

Room temp 72° F. 

Gas burned, uncorrected 0.200 cu. ft. 

Gas burned, corrected 0.2X0.965X0.996=0. 192 cu. ft. 

tt *■ i 3.164X9.44X3.9 68 A17T5 + 
Heating value c\~Tq9 = 617 B.t.u. 

Had the English system of weights and measures been used 
throughout, the calculation would have been simplified by the 
elimination of the factor 3.968 and would have become 



Gas burned, corrected =0.192 cu. ft. 

Water heated = 6 . 97 lb. 

Rise in temp, of water =17.0° F. 

tt *■ i 6.97X17.0 ft1 „. 

Heating value = — 1Q2 — =617 B.t.u 

12. Gross and Net Heat Values. — The method of calcula- 
tion of the preceding section gives the amount of heat which would 
be imparted to the calorimeter if the products of combustion 
were cooled in the instrument to the temperature of the gas and 
air which were burned and escaped from the instrument with the 
same amount of moisture which they brought to it. It gives the 
maximum utilizable heat and so is often called the gross heat 
value. In the absence of any specification to the contrary 
the term heat value is to be understood to mean gross heat 
value. 

In most industrial operations the combustion gases are not 
cooled to room temperature before escaping from the apparatus 



102 GAS AND FUEL ANALYSIS 

and therefore some of the heat of the gas is wasted. This is due 
to a lack of efficiency of the apparatus and varies with individual 
conditions There are so many industrial operations, however, 
where the water formed in combustion escapes as steam and the 
latent heat of steam formation is so large when compared with the 
amount of heat required to raise the temperature of fixed gases 
or of water or steam through moderate temperature intervals 
that the value of the latent heat is frequently deducted from the 
gross heating value. The resulting lower value is called the net 
heating value. The heat absorbed when one gram of water at 100° 
C. changes to steam at the same temperature is 0.536 Calories. 
The heat absorbed in the change of liquid water at 10° C. to 
vapor at 10° C. is very closely 0.600 Calories. This latter figure 
is usually employed in calculating the net heating value which is 
obtained by multiplying the number of cubic centimeters of con- 
densed water dripping from the calorimeter during the combustion 
of a cubic foot of gas by 0.6, and 3.968 to convert into British 
thermal units and then subtracting this value from the gross 
heat value in British thermal units per cubic foot. The method 
of calculating the net heating value in the test reported in the 
preceding section is as follows: 

Meter reading at start 21 . 200 

Meter reading at close 22 . 100 

Gas burned . 900 cu. ft. uncorrected 

Gas burned corrected, 0.9X0.965X0.996=0.86 cu. ft. 
Condensed water collected, 21.8 c.c. 

21.8 
Condensed water formed per cu. ft. gas x-^« =25.4 c.c. 

Latent heat of condensed water 25.4X0.6X3.968 = 60 B.t.u. 
Net heating value of gas 617-60 = 557 B.t.u. 

13. Accuracy of Method. — The accuracy of the Junkers 
Calorimeter was thoroughly investigated in 1905 by Immenkotter 1 
and in 1908 and in subsequent years by the Committee on Cal- 
orimetry 2 of the American Gas Institute which made a com- 
parative study of the Junkers Calorimeter as compared with other 

1 Jour, fur Gasbel.f 48, 736. 

2 Proc. Am. Gas Inst., 1908, 285; 1909, 148; 1912, 65. 



HEATING VALUE OF GAS 103 

continuous flow instruments. Both investigations agree as to 
the substantial accuracy of the Junkers calorimeter. 
The sources of error are as follows : 

1. Registration of gas volume. 

2. Measurement of temperature. 

3. Measurement of water heated. 

4. Incomplete combustion. 

5. Sensible heat and uncondensed water vapor escaping in 
combustion gases. 

6. Heat lost by radiation. 

Errors in Registration of Gas Volume. — If the meter is in good 
condition and is calibrated after the water level has been ad- 
justed the error of the meter need not exceed one-tenth of 1 per 
cent. If these precautions are neglected the error may be large. 
The error of observation will be about one small division of the 
large scale corresponding to 1 part in 200 or 0.5 per cent, error 
in a test as ordinarily run. 

Errors in Measurement of Temperature. — If the thermometers 
are accurately calibrated, the water supply of constant tempera- 
ture and the consumption of gas and its heat value constant dur- 
ing a test, there should be practically no instrumental error. If 
the constancy of any of these conditions is upset there will be 
errors due partly to lag in the thermometers which do not instantly 
respond to the changed condition. An error which is negligible 
except in the most accurate work is that caused by the different 
temperature of the bulb and the stem of the thermometer. There 
will be no correction for the emergent stem of the inlet thermom- 
eter if the inlet water is at room temperature. If the room temper- 
ature is 70° F., and the temperature of the outlet water is 90° F., 
an addition of from 0.07 to 0. 10° F. , should be made to the observed 
reading of the outlet thermometer, the exact amount depending 
on the depth to which the stem of the thermometer is immersed 
in the water. Detailed tables giving these corrections may be 
found in the Proceedings of the American Gas Institute for 1912 
and also in a pamphlet published by the American Gas Institute 
entitled Directions for Erecting and Operating Gas Calorimeters. 
A more important error due to changed conditions during a test 
results from the large volume of water always contained in the 



104 GAS AND FUEL ANALYSIS 

calorimeter. The Junkers calorimeter contains approximately 
1500 grm. of water so that if a 2000 c.c. cylinder is being used to 
catch the water, it will have become three-quarters full before any 
of the water whose temperature at the inlet has been taken reaches 
the thermometer at the outlet. It will be evident that the larger 
the volume of water in the calorimeter the greater is the possible 
error from this source. The error in making a single reading of 
the thermometers should be less than a tenth of a degree and the 
mean error of a series of seven observations should not be over 
0.05°. On a rise of ten degrees this corresponds to 0.5 per cent. 
This average of seven readings will not give the correct mean 
temperature of the water unless the individual readings differ 
from each other only by a few tenths of a degree. 

Errors in Determination of Mass of Water Heated. If the 
water is measured in a two liter cylinder the error of the ob- 
servation will hardly be less than 10 c.c. or 0.5 per cent, and may 
be twice as great. The error in weighing the water should be less 
than 0.1 per cent, but an error of a second in terminating the 
experiment means 25 c.c. of water. This is a greater time error 
than necessary but the probable error in this process will be 0.5 
per cent. 

Error Due to Incomplete Combustion. — When the calorimeter is 
properly adjusted, this error should vanish. 

Errors Due to Sensible Heat and Uncondensed Water Vapor 
Escaping in Combustion Gases. — As the gases pass down through 
the calorimeter they meet water of progressively lower tempera- 
ture until just before leaving the calorimeter they are surrounded 
by water of the temperature recorded by the inlet thermometer. 
They should therefore leave the instrument at a temperature 
within a few degrees of that of the inflowing water. With a 
theoretical air supply the error from this loss of sensible heat in 
the dry gas is less than 0.3 B.t.u. per degree of temperature 
difference per cubic foot of gas burned. According to the report 
made to the American Gas Institute, 1 the actual errors observed 
as due to this source were only 0.5 B.t.u. per degree per cubic 
foot even when the temperature of the inlet water was far from 
that of the room. The actual figures recalculated slightly are 
given below. 

1 Proc. Am. Gas Inst., 1909, 168. 



HEATING VALUE OF GAS 



105 



Temp, 
inlet 
water 


Temp. 

exhaust 

gases 


Difference between 

temp, exhaust gas 

and inlet water 


. Error in heat value 
due to sensible heat 
of dry gases of com- 
bustion, B.t.u. 


Error per 

degree 
difference 


Deg. F. 










39 


45.6 


+6.6 


+3.7 


0.56 


49 


54.2 


+5.2 


+2.7 


0.52 


59.6 


63.2 


+3.6 


+ 1.8 


0.50 


70.4 


72.4 


+2.0 


+ 1.0 


0.50 


80.5 


81.5 


+ 1.2 


+0.3 


0.23 


89.3 


88.6 


-0.7 


-0.5 


0.70 



The error due to water vapor in the exhaust gases may be 
more serious. The exhaust gases always leave the calorimeter 
saturated with water. The gas burned having passed through a 
wet meter is also practically saturated with water. The air for 
combustion, whose theoretical volume for illuminating gas is 
roughly six times the volume of the gas, and whose actual volume 
may be twice that, is drawn from the room and may vary widely 
in humidity. The maximum error which can thus be introduced 
may be indicated by the following calculation. It is assumed 
that one volume of gas is burned with six volumes of air and that 
the volume after combustion contracts to six volumes. The 
water formed in combustion will remain in the vapor form so far 
as the gases can hold it and the remainder will condense in the 
calorimeter. The one volume of gas burned entered the calor- 
imeter saturated with water so that only additional water to 
saturate 5 cu. ft. need come from combustion. The weight of 
water vapor per cubic foot of gas will vary with the temperature 
as shown in the following table. 

Wt. vapor in 
Temp. • mixed cu. ft. 

gas and vapor 

32° F 0.000304 lb. 

42° F 0.000440 lb. 

52° F 0.0006271b. 

62° F 0.0008811b. 

72° F 0.0012211b. 

82° F 0.001667 1b. 

92° F 0.002250 lb. 

The following examples will serve as an illustration of the use 
of these figures. 



106 GAS AND FUEL ANALYSIS 

(1) Assume that the air enters at 62° and 50 per cent, saturated 
with water vapor, the gas enters at 62° saturated with moisture 
and the exhaust gases escape at 82°. 

Moisture brought in 6 cu. ft. air at 0.00044=0.00264 lb. 
Moisture brought in 1 cu. ft. gas at 0.00088 = 0.00088 lb. 

6T00352 
Moisture carried out by 6 cu. ft. gas at 0.00166 0.01000 
Excess of moisture supplied from water of 

combustion . 00648 lb. 

Latent heat =1070 B.t.u. per lb. 
Heat lost =0.00648X1070 = 6.9 B.t.u. 

This is an unusually large error since there is no need of letting 
the exhaust gases escape at such a high temperature. If they 
had escaped at 72° the error from this source would have been only 
4.1 B.t.u. If they had escaped at 62° the error would have been 
only 1 .9 B.t.u. If they had escaped at 52° or 10° below room tem- 
perature the error would have been almost zero. 

This error is present in almost all operations but when care is 
taken to have the temperature of the exhaust gases a few degrees 
below that of the room the error should not be over 3 B.t.u. 
It will usually make the result too low but in cases where the room 
is warm and the air nearly saturated with water it may be in the 
other direction. 

The most accurate results are obtained by keeping the tempera- 
ture of the gas and the exhaust at room temperature and correct- 
ing for the humidity of the air according to the following table 
compiled by the Bureau of Standards. 1 Under these conditions 
the error will be about 1 B.t.u. Before using this table the humid- 
ity of the air must be determined as directed in the following 
Section. The corrections are expressed in B.t.u. 's and are to be 
added where the sign is + and subtracted where it is — . 

1 Proc. Am. Gas. Inst., 7, 223 (1912). 



HEATING VALUE OF GAS 



107 



CORRECTIONS TO OBSERVED HEAT TO GET TOTAL HEAT 

VALUE. AIR, GAS AND EXHAUST MUST BE AT THE 

SAME TEMPERATURE 

If 7 volumes of air per volume of gas are used 



Humidity 


Room temperatures 


per cent. 


65° 


70° 


75° 


80° 


85° 


90° 


10 


+4.8 


+5.7 


+6.7 


+7.9 


+9.2 


+ 10.5 


20 


+4.1 


+4.9 


+5.7 


+6.8 


+7.8 


+ 9.0 


30 


+3.4 


+4.1 


+4.7 


+5.6 


+6.5 


+ 7.4 


40 


+2.7 


+3.2 


+3.7 


+4.5 


+5.2 


+ 5.9 


50 


+2.0 


+2.4 


+2.8 


+3.4 


+3.8 


+ 4.3 


60 


+ 1.3 


+ 1.6 


+ 1.8 


+2.2 


+2.5 


+ 2.8 


70 


+0.6 


+0.8 


+0.8 


+ 1.0 


+ 1.2 


+ 1-2 


80 


-0.1 


±0.0 


-0.1 


-0.1 


-0.1 


- 0.3 


90 


-0.8 


-0.9 


-1.1 


-1.3 


-1.5 


- 1.9 


100 


-1.6 


-1.8 


-2.0 


-2.4 


-2.8 


- 3.4 



Loss of Heat by Radiation. — The calorimeter is protected against 
interchange of heat with the outside air by an insulating air 
chamber enclosed in a polished metal jacket. The efficiency 
of this protection is given in the report of the Committee on 
Calorimetry of the American Gas Institute for 1908 as 99.5 
per cent. The metal jacket should be kept bright in order to 
maintain this efficiency. 

Accuracy of the Process as a Whole.- — None of the various 
preceding sources of error need amount to over 0.5 per cent. 
They will partially offset one another. When great care is taken 
the total error may not be over 1 per cent. Under ordinary 
conditions it is not safe to assume that the error will be less than 
2 per cent. 

14. Determination of Humidity of Air. — The following direc- 
tions for the measurement of atmospheric moisture are given by 
the U. S. Weather Bureau. 1 The most reliable instrument for 
this purpose is the sling, or whirled psychrometer. In special 
cases rotary fans, or other means, may be employed to move the 
air rapidly over the thermometer bulbs. In any case satisfactory 
results cannot be obtained from observations in relatively 
stagnant air. A strong ventilation is absolutely necessary to 
accuracy. 

1 U. S. Dept. Agriculture, W. B. No. 235, Psychrometric Tables. 



108 



GAS AND FUEL ANALYSIS 




Fig. 25.- 
Sling psy- 
chrometer. 

bulb first. 



The sling psychrometer consists of a pair of ther- 
mometers, provided with a handle as shown in Fig. 
25, which permits the thermometers to be whirled 
rapidly, the bulbs being thereby strongly affected 
by the temperature of and moisture in the air. The 
bulb of the lower of the two thermometers is cov- 
ered with thin muslin, which is wet at the time an 
observation is made. 

It is important that the muslin covering for the 
wet bulb be kept in good condition. The evapora- 
tion of the water from the muslin always leaves in 
its meshes a small quantity of solid material, which 
sooner or later somewhat stiffens the muslin so that 
it does not readily take up water. This will be the 
case if the muslin does not readily become wet after 
being dipped in water. On this account it is de- 
sirable to use as pure water as possible, and also 
to renew the muslin from time to time. New mus- 
lin should always be washed to remove sizing, etc., 
before being used. A small rectangular piece wide 
enough to go about one and one-third times around 
the bulb, and long enough to cover the bulb and 
that part of the stem below the metal back, is cut 
out, thoroughly wetted in clean water, and neatly fitted 
around the thermometer. It is tied first around 
the bulb at the top, using a moderately strong 
thread. A loop of thread to form a knot is next 
placed around the bottom of the bulb, just where 
it begins to round off. As this knot is drawn tighter 
and tighter the thread slips off the rounded end of 
the bulb and neatly stretches the muslin covering 
with it, at the same time securing the latter at the 
bottom. 

To make an observation, the so-called wet bulb 
is thoroughly saturated with water by dipping it 
into a small cup or wide-mouthed bottle. The ther- 
mometers are then whirled rapidly for fifteen or 
twenty seconds; stopped and quickly read, the wet 
This- reading is kept in mind, the psychrometer imme- 



HEATING VALUE OF GAS 109 

diately whirled again and a second reading taken. This is re- 
peated three or four times, or more, if necessary, until at least 
two successive readings of the wet bulb are found to agree very 
closely, thereby showing that it has reached its lowest tempera- 
ture. A minute or more is generally required to secure the cor- 
rect temperature. In whirling and stopping the psychrometer 
the arm is held with the forearm about horizontal, and the hand 
well in front. A peculiar swing starts the thermometers whirling, 
and afterward the motion is kept up by only a slight but very 
regular action of the wrist, in harmony with the whirling ther- 
mometers. The rate should be a natural one, so as to be easily 
and regularly maintained. If too fast, or irregular, the ther- 
mometers may be jerked about in a violent and dangerous man- 
ner. The stopping of the psychrometer, even at the very highest 
rates, can be perfectly accomplished in a single revolution, when 
one has learned the knack. This is only acquired by practice, 
and consists of a quick swing of the forearm by which the hand 
also describes a circular path, and, as it were, follows after the 
thermometers in a peculiar manner that wholly overcomes their 
circular motion without the slightest shock or jerk. The ther- 
mometers may, without very great danger, be allowed simply to 
stop themselves; the final motion in such a case will generally be 
quite jerky, but, unless the instrument is allowed to fall on the 
arm, or strikes some object, no injury should result. 

The tables from which humidity may be calculated form 
Table IV of the Appendix and give the data for a barometric 
pressure of 29.0 inches of mercury. Their use is illustrated by 
the following example. 

Air temperature t = 75.0° F. 

Wet bulb reading t' = 66.0° F. 

t-t' = 9.0° F. 

In table opposite 75° in column 9.0 is found 63. 
Relative humidity = 63 per cent. 

If the barometric pressure had not been 29 in. a slight error, 
would have been introduced whose magnitude may be judged 
from the following examples of the same problem at different 
barometric pressures. 



110 GAS AND FUEL ANALYSIS 

Barometric pressure 30 Relative humidity 63 

Barometric pressure 27 Relative humidity 63 

Barometric pressure 25 Relative humidity 64 

The Weather Bureau report 235 referred to above gives fuller 
tables and may be obtained from the Bureau for 10 cents. 

15. Non-continuous Water Heating Calorimeters. — In the 
third edition of his Gas Analysis, Hempel described a calorimeter 
where a volume of about a liter of gas was measured in a glass 
cylinder, passed through a small burner and burned in a stream 
of oxygen within a calorimeter containing a known mass of water. 
The rise in temperature of the water gave the data for the calcu- 
lation of heat value, after the instrument had been calibrated by 
the combustion of hydrogen. 

The Graefe calorimeter is a more recent commercial instrument 
of the same general type but somewhat larger. The instrument 
is rather crudely constructed and allows the exhaust gases to 
escape at an unduly high temperature so that it is necessary to 
calibrate it against some standard calorimeter. An inherent 
defect in calorimeters of this type comes from the increasing 
temperature of the exhaust gases as the test proceeds and the 
water of the calorimeter becomes warmer. 

The Parr 1 calorimeter aims to compensate for this error and 
errors due to moisture in the exhaust gases by providing two du- 
plicate calorimeters, one of which runs on pure hydrogen while 
the other is testing the unknown gas. The variation from the 
correct result shown by the hydrogen calorimeter is taken as the 
correction to be applied to the other result. The Committee on 
Calorimetry of the American Gas Institute in its 1912 report 
states that this calorimeter if properly operated gives correct 
results but that it is rather complicated in construction and 
requires more skill for its proper operation than the other types. 
The instrument gives gross heating values only. 

The Doherty calorimeter is a compact instrument which meas- 
ures the gas in an annular cylinder surrounding the combustion 
chamber and its water jacket. The gas is displaced by the 
warmed water which has flowed through this water jacket or heat 
absorption chamber, and thermometer readings are taken as the 

1 J. Ind. and Eng. Chem., 2, 337 (1910). 



HEATING VALUE OF GAS 



111 



water level passes fixed points on the gage glass. No meter is 
required and the water is neither weighed nor measured. The 
Committee on Calorimetry of the American Gas Institute in 
its 1912 report states that this calorimeter when operated properly 
gives the same efficiency as the Junkers calorimeter. 

16. Automatic and Recording Gas Calorimeters. — The form- 
ula for the calculation of the heating value of a gas as given in 

§ 11 of this chapter is H.V. = E^JZ^ 



It is evident that if the 



m 



ratio — can be kept a constant and t can also be kept constant 

that the heating value can be readily determined from a single 
reading of t' or can be continuously determined by a recording 
thermometer showing the temperatures of the outlet water. In 

the Junkers continuous calorimeter the ratio — is kept constant 

by passing both gas and inlet water through meters whose drums 
are geared together by a chain forcing them to always rotate 
proportionately. There are various other types of automatic 
calorimeters. In every case they should be checked occasionally 
by a direct determination with a standard instrument. 

17. Calculation of Heating Value from Chemical Composi- 
tion. — If the heat value and the proportion of each constituent 
in a mixed gas were accurately known, it would be possible to 
calculate the heating value of the mixture with entire accuracy. 
The following table gives the usual values in Calories per gram 
molecule and also the values recalculated by Earnshaw 1 to 
British thermal units at 60° F. and 30" of mercury pressure. 



Gas 


Formula 


Calories per 
gram molecule 


B. t. u.'spercu. 
ft. at 60° and 30" 


Hydrogen 

Carbon monoxide 

Methane 


H2 

CO 

CH 4 

C2H6 

C3H8 

C4H10 .... 

C<H 4 

C3H6 

C 4 H 8 

C2H2 

Cell 6 


68,360 
67,960 
211,930 
370,440 
529,210 
687,190 
333,350 
492,740 
650,620 
310,050 
799,350 


326.2 

323.5 

1009 . 2 


Ethane 


1764.4 


Propane 


2521.0 


Butane 


3274.0 


Ethylene 

Propylene 

Butylene 

Acetylene 

Benzene 


1588.0 
2347.2 
3099 . 2 
1476.7 
3807.4 



1 Jour Franklin. Inst., 146, 161 (1898). 






112 GAS AND FUEL ANALYSIS 

If each constituent in the gas were known, the heating value 
calculated from this data would probably give accurate results. 
However, when it is noted that among the defines, propylene 
has a heating value approximately 50 per cent, greater than ethy- 
lene, and butylene a heating value almost double that of ethylene 
it will be seen that there is dangerous latitude for arbitrary 
assumptions as to the constituents of the olefines. When the 
" illuminants " as reported include not only the olefines but ben- 
zene the error involved in an arbitrary assumption of the mean 
heat value becomes still greater. The varying members of the 
methane series also possess widely differing heating values. 
Earnshaw, in the reference cited gives an analytical method 
for determining the mean composition of the olefines and for 
differentiating between methane and ethane. The method is, 
however, difficult analytically, and the results when obtained 
are not entitled to the degree of confidence which pertains to 
those obtained directly in a calorimeter. 

The probable error involved in this method of calculating the 
heating value of gas (unless Earnshaw' s complex analysis is 
followed out) is about 5 per cent. In the case of carburetted 
water gas it is still higher. In the case of producer gas where the 
total percentage of hydrocarbon is low and where all suspended 
tar particles have been removed the results are more accurate. 



CHAPTER VIII 
CANDLE POWER OF ILLUMINATING GAS 

1. Introduction. — Photometry deals with the measurement of 
the intensity of light. The term light as used here includes only 
those rays which excite vision in the human eye, which thus 
necessarily becomes the final arbiter in photometric tests. The 
eye cannot estimate absolutely the amount of light which stimu- 
lates it. It can compare roughly the intensity of illumination 
from two sources and it can determine with more precision when 
the intensities from two sources are the same. In the sense in 
which it is here used, photometry consists in the comparison of 
two lights, one of which is a standard. The photometer is a 
device which assists the eye in determining when the two lights 
are of the same intensity. The intensity of light entering the pho- 
tometer is changed by varying the distance between the photom- 
eter and the light, the intensity of light from a given source varying 
inversely as the square of the distance. When the adjustments 
have been made so that the intensity of light impinging on the 
photometer from the two sources is the same, as shown by the 
equal illumination of the two photometer faces, the ratio of the 
unknown light to the standard light becomes mathematically 
calculable from the relative distances of the lights from the point 
of equal illumination. The value of luminous intensity is in 
English-speaking countries and in France expressed in candle- 
power. 

2. Method of Rating Candle-power. — The light emitted from 
a single incandescent particle would illuminate uniformly every 
point of an enveloping sphere and the intensity of illumination 
might be measured equally well at any point on the sphere. 
When the light to be measured comes from a surface of finite size 
as is always the case in practice, there is interference with the free 
path of the light waves from a single particle in one or more direc- 
tions so that the illumination of the enveloping sphere is no longer 

8 113 



114 GAS AND FUEL ANALYSIS 

uniform. It is possible by the use of reflecting mirrors to deter- 
mine the illumination at various points on the circumference of a 
polar circle and to plot from this data a curve showing the dis- 
tribution of light at various angles. Methods of this sort are 
often resorted to in a study of illumination where it is desired to 
determine the value of a light source for a particular purpose. 
This method is, however, rarely followed where it is simply a 
question of testing the quality of the gas. The simpler custom of 
taking the horizontal candle-power given by a conventionalized 
burner under conventional conditions as indicating the value of 
the gas, has become well established. 

3. The Bar Photometer. — The bar photometer consists of 
a graduated bar which carries at one end a standard light and at 
the other end the test light. Upon the bar slides a carriage with 
an apparatus for comparing the illumination from the two sources. 
The carriage is to be moved back and forth until the point is 
found where the illumination from the two lights is equal, and its 
position on the graduated bar recorded. If now the distance of 
the comparison box from the standard light be called "a" and 
that from the unknown light "b," then the illumination of the 
unknown as compared with the standard light is expressed by the 
proportion, 

unknown _b 2 

standard a 2 

There are many modifications of this type of photometer but 
all involve the four essentials: a standard light, the unknown 
light, a photometric screen and a means of measuring the distance 
of each light from the comparison box. It is customary to have 
the two lights fixed at opposite ends of the bar, in which case the 
sum of a+b in the preceding formula is a constant. Some- 
times however the standard lamp is placed on a sliding carriage 
connected by a rigid link with the photometric screen so that the 
distance " a" of the formula becomes a constant. A modification 
of the bar photometer in use in England is the table photometer 
where the two lights and the comparison box are all rigidly fast- 
ened at the points of a triangle. Comparison is effected by vary- 
ing the rate of combustion of the gas being tested until equality 
of illumination is reached. Its candle-power is then mathematic- 



CANDLE POWER OF ILLUMINATING GAS 115 

ally determined. This method of determining candle-power is 
not in use in Germany or America. 

The various essential parts of a bar photometer will be con- 
sidered separately and the details of its operation will then be 
described. 

4. Standard Light. — The early photometrists used as their 
standards candles of varying size. In 1860, the English parlia- 
ment adopted as standard the sperm candle 7/8 in. in diameter 
and burning at the rate of 120 grains per hour. In 1884, Hefner 
v. Alteneck brought out the amylacetate lamp which has become 
the most generally used standard for testing the candle-power of 
gas. The Harcourt 10 candle pentane lamp was proposed in 1898 
and has been adopted as the official source of light by the Gas 
Referees of London. It has many advantages. All of these 
flame standards vary materially in candle-power with change 
in atmospheric conditions and are, for scientific work, to be cor- 
rected to standard conditions of temperature, pressure, humidity 
and percentage of carbon dioxide in the air. In ordinary work 
when used in measuring candle-power of gas flames they are how- 
ever not thus corrected but the assumption is made that the stand- 
ard light and the gas light are equally affected by atmospheric 
conditions. 

The only satisfactory standard not affected by atmospheric con- 
ditions is the incandescent electric lamp. Incandescent lamps 
properly aged may be bought with the certificate of the Bureau of 
Standards and furnish the most reliable photometric standards 
when used under proper conditions. These conditions, however, 
require that the lamp shall be supplied with current at perfectly 
definite voltage from a large storage battery equipped with suit- 
able rheostats and electrical measuring instruments so that the 
installation is an expensive one, and is used only in research 
laboratories. When the incandescent electric standard is used 
in the photometry of gas flames correction must be made for the 
effect of atmospheric conditions on the flame. This correction 
is not infrequently as much as ten percent, and has been accu- 
rately determined for only a few of the standard lights. 

5. Photometric Units. — The international candle is the common 
unit of intensity in England, France and America, having been 
officially adopted by agreement of the government standardising 



116 GAS AND FUEL ANALYSIS 

laboratories of the three countries in 1909. Prior to that date 
the official unit in this country had nominally been the British 
Parliamentary candle but there had not been definite agreement 
as to its value. In Germany the photometric unit is the Hefner 
which equals 0.90 International Candles. Conversely 1 Inter- 
national Candle equals 1.11 Hefners. The history of the adop- 
tion of the International Candle may be found in the reports of 
the Bureau of Standards and in the Proceedings of the American 
Gas Institute. 1 

Although there is thus an international unit of light, the 
international candle, it does not follow that this unit is best 
obtained by burning any actual candle. In fact various other 
standard lights are preferable. 

6. Standard Candles. — In 1860 the Gas Referees of the City 
of London adopted as their unit the light emitted by a sperm 
candle of 1/6 lb. weight when burned at the rate of 120 grains per 
hour. From time to time they issued specifications for the manu- 
facture of candles to fulfill this requirement but were never success- 
ful in ensuring uniform quality and in 1897 entirely discontinued 
the use of candles. The Dutch Photometric Commission reported 
in 1894, after an exhaustive study, that the average light from 
a good English Parliamentary candle might exceed or fall below 
that of the average candle by nine per cent. The use of candles 
as standards is deservedly decreasing. 

When candles are to be used they are burned on a candle 
balance placed on the photometer bench. A simple form of 
balance is illustrated in Fig. 26. A long candle is cut in 
two and both halves used simultaneously. They are to be al- 
lowed to burn until the cups have formed normally and the wicks 
have bent over till the tips are glowing in the outer flame. The 
candles are then to be turned so that the glowing end of one 
wick points towards the photometer and that of the other points 
in a direction at right angles to that of the first. They should 
project 1 to 1 1/2 in. above the holder and should burn clearly and 
without guttering. When all is in readiness for a test, the 
counterpoises are adjusted so that the candles are slightly too 
heavy for a perfect balance. ' As they burn away the pointer 
on the scale falls and as it passes the zero mark the stop watch is 

1 Proc. Am. Gas Inst. 2, 454, 528 (1907): 3, 403 (1908); 4, 78 (1909). 



CANDLE POWER OF ILLUMINATING GAS 



117 



started. A 20-grain weight is then placed on the pan below the 
candles and photometric readings are made each half-minute. 
At the expiration of four and a half minutes the observer returns 
to the candle balance and stops the watch when the pointer 
again is at the zero mark, indicating that the 20 grains of sperm 
have been burned. If the candles are burning at exactly the 
proper rate the watch should show that exactly five minutes 
have elapsed. If the variation in the amount of sperm burned 
per hour is not over 5 per cent, from the standard amount it is 
permissible to make a mathematical correction, the assumption 





Fig. 26 — Candle balance. 



being that the light evolved is in direct proportion to the weight 
of candles burned. If the observed weight of sperm burned by 
the two candles is 250 grains per hour instead of 240 the value 

250 
of the light is said to be 2x^7, = 2.08 candles. If the deviation 

is greater than 5 per cent, the test must be rejected and a 
different candle used. Improper ventilation and too high a 
temperature in the photometer room will affect the burning of the 
candles. This subject is discussed in § 18. 

7. The Hefner Lamp. — The dimensions of the Hefner lamp 
have been rigidly specified by the German Reichsanstalt 1 which 

1 Jour, fur Gasbel, 36, 341 (1893). 



118 



GAS AND FUEL ANALYSIS 



will certify a lamp to be correct if it is mechanically properly 
made and gives a light which does not differ more than 2 per cent, 
from the official lamp of the Reichsanstalt. The construction 
of the lamp is shown in Fig. 27. It consists of a brass bowl 
into which a head screws carrying the German silver wick tube 
and the mechanism for controlling the height of the flame. 
The flame height is determined by a gage which clamps to the 
head-piece. The older form of gage shown at A consists of two 
sights, one on each side of the flame. The newer Kruss optical 
gage shown at C consists of a ground glass screen and a magnify- 




Fig. 27. — Hefner lamp. 



ing lens which allows more delicate adjustment of the flame tip 
to the horizontal line across the gage. Each lamp is provided 
with a control gage shown at B which fits over the wick tube 
and sits squarely on the head-piece. With the control gage in 
this position and the lamp level an observer looking toward the 
light should see through the openings D a very fine ray of light 
less than 0.1 mm. wide between the top of the wick tube and the 
control gage, and looking through the optical gage should see 
the cross-hair in exact coincidence with the broad top of the 
control gage. The wick tube is screwed into the head-piece 
and if it becomes necessary to change its height the control gage, 



CANDLE POWER OF ILLUMINATING GAS 119 

inverted, is to be pushed down the wick tube and used as a handle. 
The exact material of which the wick is made is not of importance 
but it must fill the tube snugly but not tightly. It is best to use 
only that furnished by the manufacturers. The amyl acetate 
must be of good quality and certified to be fit for photometrical 
purposes. The German Gas Association sells properly certified 
amyl acetate in one liter bottles. 

In using the Hefner lamp the bowl is to be filled about two- 
thirds full of amyl acetate and after the wick has been moistened 
by capillary action it is to be screwed somewhat above the wick 
tube and cut squarely off. The lamp is then to be lighted and 
allowed to burn at least ten minutes with occasional regulation 
of the flame height before a test is commenced. The temperature 
of the photometer room should be between 60° and 70° F. The 
lamp is to sit on a horizontal support in a room free from drafts 
and adequately ventilated. 

The flame height of the Hefner lamp is to be carefully adjusted 
since a deviation of 1 mm. from the correct flame height of 40, 
introduces an error of about 3 per cent. It is the luminous tip 
of the flame which is to be 40 mm. high. With the Kruss optical 
gage the frosted glass cuts out the almost colorless outer flame so 
that there is no possibility of confusion. With the older Hefner 
gage the luminous tip should appear tangent to the lower edge 
of the sighting plane. 

If the lamp is used only infrequently it should be emptied 
after use and both lamp and wick should be washed with alcohol. 
It is wise to throw away the old amyl acetate and clean the lamp 
in this manner at intervals even when it is in frequent use since 
the amyl acetate decomposes somewhat on standing. 

The Hefner lamp gives a light of 0.9 international candles 
when burned in pure air under 760 mm. barometric pressure and 
containing 8.8 liters of water vapor per cubic meter. Although 
atmospheric conditions must be controlled and correction made 
in exact scientific work corrections are usually omitted in taking 
candle-power of gas on the assumption that atmospheric condi- 
tions affect the Hefner lamp and the gas burner to a similar de- 
gree. The errors involved in this assumption are discussed briefly 
in § 18. The Hefner lamp is a very widely used standard. It is 
portable, cheap, and accurate. Its disadvantage is its low candle- 



120 



GAS AND FUEL ANALYSIS 



8. The Pentane Lamp. 



power, and the tendency of the flame to flicker, especially at 
summer temperature. 

— The 10 candle pentane lamp or 
Harcourt lamp was adopted as stand- 
ard by the London Gas Referees in 
1898. 1 

Fig. 28 shows this lamp with some 
improvements in details recommended 
by the Bureau of Standards and added 
by the American manufacturers. In 
this lamp air entering at A passes over 
pentane and becomes saturated with 
pentane vapor. The air-gas so formed 
descends by gravity to an Argand 
burner B enclosed in a metal hood. 
The flame is drawn into a definite 
form and the top of it is hidden from 
view by a long brass chimney C. The 
chimney is surrounded by a larger 
brass tube D in which air, warmed by 
the chimney, rises and descends 
through the tube E, which is also the 
main standard of the lamp, to the cen- 
ter of the Argand burner where it aids 
in the combustion of the gas. The 
lamp may be obtained with the cer- 
tificate of the Bureau of Standards. 

Before using the lamp the satu- 
rator is to be filled about two-thirds 
full of pentane and both cocks on the 
saturator are to be closed. As pen- 
tane is very volatile and mixtures of its vapor and air within 
certain proportions are explosive care must be taken that no 
flames are burning in the room while the lamp is being filled. 
The inner chimney above the burner must be centered by 
the adjusting screws, turned so that the mica window is away 
from the photometer box and set at the proper height by plac- 
ing on the burner the 47 mm. block which accompanies the 
x Jour. of Gas Lighting, 71, 1253 (1898). 




Fig. 28. — 10 candle power 
pentane lamp. 



CANDLE POWER OF ILLUMINATING GAS 121 

lamp, and lowering the chimney till it rests lightly on the block. 
To prepare the lamp for lighting, open the outlet cock on the 
saturator and the drip cock. This will fill the feed pipe with pen- 
tane vapor and air. Open the inlet cock on the saturator, close 
the drip cock, open the regulating cock at the burner and light the 
gas at once. It requires about fifteen minutes for the flame to 
become constant and during this period the top of the flame should 
be kept approximately on the cross bar of the mica window. 
The lamp should be set for maximum luminosity which condition 
is attained when the flame is just high enough so that the non- 
luminous upper portion is cut off from the photometric screen by 
the chimney. In case of doubt the proper setting may be deter- 
mined by lighting the gas flame at the other end of the bench 
and determining with the photometer the setting of the lamp 
which gives maximum illumination. 

In leaving the lamp after a test both the inlet and the outlet 
cocks of the saturator should be closed. After about a gallon of 
pentane has been burned the liquid remaining in the saturator 
should be emptied out and thrown away. 

9. Secondary Standards of Light. — The Hefner lamp, the 10 
Candle Pentane lamp and, to a lesser degree, standard candles 
are primary standards since they are readily reproducible. There 
are various secondary standards which are convenient to use 
when frequent candle-power determinations are to be made but 
which must be standardized at intervals by direct comparison 
with a primary standard. Most of these standards are based on 
the fact that the brightest portion of a lamp flame is of almost 
constant luminosity. 

The Edgerton Standard burner consists of a Sugg "D" burner 
provided with a glass chimney 1 3/4 in. in diameter and 7 in. 
high. Outside of this glass chimney is a brass sleeve with a 
horizontal slot 13/32 of an inch high through which the light 
passes to the photometer. This is nominally a five candle-power 
standard but will actually vary from four to seven candles. 
After the value with a given gas has been fixed it will not vary 
much if the candle-power of the gas feeding it does not vary over 
two candles. The chimney must be cleaned frequently and the 
lamp restandardized each time a new chimney is put into service. 

The Elliot lamp is a student lamp of special design with a 



122 



GAS AND FUEL ANALYSIS 



flat wick and a rather large chimney and a screen which cuts off 
all but the desired portion of the flame. The lamp uses kerosene 
as its fuel and is nominally a ten candle-power lamp. Its illu- 
minating value with a single lot of good kerosene is of very satis- 
factory constancy. 

10. Standard Gas Burners. — At the time when gas testing 
commenced to be standardized the Argand burner was the form 
in common use. This type was therefore naturally adopted as 
the standard. It was also recognized that it was only right to 





Fig. 29.— D Argand 
burner. 



Fig. 30.— Metropolitan 
No. 2 Argand burner. 



test the gas in a burner which was adapted to it and therefore 
various standards came into vogue in England, such as the Sugg 
D Argand illustrated in Fig. 29, which is intended for gases 
of less than 16 candle-power. The Sugg F burner is intended for 
gases of 16-20 candle-power. 

In 1905, in connection with a readjustment of the price and 
candle-power of the gas supplied in London the Gas Referees 
were directed by Parliament, to use a burner adapted to obtain 
from the gas the greatest amount of light when burned at the 
rate of five cubic feet per hour. In accordance with these instruc- 



CANDLE POWER OF ILLUMINATING GAS 123 

tions the Gas Referees adopted the Metropolitan No. 2 Burner 
shown in Fig. 30. This burner differs from the older types 
mainly in having an adjustable air supply to the center of the 
burner. The burner is designed for all qualities of gas up to 20 
candle-power. When lighting the burner the air regulating disc 
A is to be screwed down so that the full supply of air passes to the 
burner, and the burner is to be adjusted to approximately the five 
cubic foot rate. After allowing it to burn for fifteen minutes to 
become thoroughly warm the gas is to be adjusted carefully 
to the rate of 5 cu. ft. an hour, after which the air regulator is to 
be screwed upwards until the flame rises in the chimney as high 
as possible without smoking. The Metropolitan No. 2 Argand 
gives results materially higher than the ordinary Argand on 
gases of low candle-power. 

Bray's No. 7 Slit Union burner is frequently used with car- 
buretted water gas of more than 20 candle-power. The rate of 
gas consumption is as usual adjusted to 5 cu. ft. an hour. 

11. The Bunsen and Leeson Photometric Screens. — The 
Bunsen photometric disc dates from 1841 and in its simplest 
form consists merely of a sheet of paper with a grease spot in the 
center. This is mounted so that it may be moved back and forth 
between the two lights. When looking toward the stronger light 
the translucent grease spot appears bright. As the carriage is 
slowly moved away from the stronger light the constrast between 
the spot and the surrounding paper diminishes and almost dis- 
appears when equality of illumination is reached. If the carriage 
is moved still further in the same direction the grease spot stands 
out dark against the white background. The paper screen is 
usually mounted in a box as shown in Fig. 34 where by an 
arrangement of mirrors the observer standing in front of the 
instrument may see both sides of the screen at once. This form 
of apparatus is still frequently used. 

The Leeson star disc is a modification of the Bunsen screen. 
It consists of a piece of opaque paper from whose center is cut 
a star and which is pressed between two sheets of translcuent 
paper. It is a decided improvement on the Bunsen screen. 

12. The Lummer-Brodhun Photometric Screen. — This is a 
very accurate form of photometer which is shown diagrammatic- 
ally in Fig. 31 and in perspective in Fig. 32. It consists 



124 



GAS AND FUEL ANALYSIS 



of a series of reflecting surfaces and prisms which direct light rays 
from the two sources into a telescope tube. Light entering from 
the two opposite sources R and L is diffusely reflected by the 




Fig. 31. — Diagram of Lummer-Brodhun photometric screen. 

opaque plaster of paris disc P onto the mirrors Mi and M 2 and 
by them to the prisms AB. The prism A has most of its hypothe- 




Fig. 32. — Lummer-Brodhun photometric screen. 

nusal face ground away, only- a small circular plane being left in 
the center. The two prisms are clamped closely together and 
become optically homogeneous over this small circular area shown 



CANDLE POWER OF ILUMINATING GAS 



125 




Fig. 33.- 
Lummer -B r o d h u n 
contrast photomet- 
ric screen. 



at ab. Of the light coming from L only that reaches the telescope 
which passes through this circular spot, the path of the rays being 
shown from L 2 . Of the light from R, that which strikes the spot 
ab passes on undeflected and is absorbed by the black walls of the 
box. The path of these rays is shown from R 2 . The other rays 
suffer total reflection into the telescope as shown in the rays from 
Ri. The image in the telescope appears, therefore, as a circular 
spot illuminated from L in a circular field illuminated from R. In 
this equality photometer when the illumination from the two 
sources is identical the spot and the field are 
not to be distinguished from one another. 

In the Lummer-Brodhun contrast photom- 
eter advantage is taken of the physiological 
fact that the eye is able to perceive a smaller 
degree of difference in contrast than difference 
in brightness. By suitably cutting the prisms 
the image in the telescope is divided into four 
portions as shown in Fig. 33. In this figure 
the shaded trapezoidal space A' is illuminated 
from the same source as the shaded semi-circular area A. Simi- 
larly B and B' are illuminated from the same source. However, 
although the areas A and A' are illuminated from the same source, 
they are not equally illuminated, for through the interposition of 
a plate of glass before A' it receives about four per cent, less light 
than A. B' is in the same way and to the same degree less 
brilliantly illuminated than B. 

If, now, the light from the two sources is exactly the same both 
in intensity and color the semi-circular fields A and B will be 
identically illuminated and will not be distinguishable from one 
another. The trapezoidal figures A' and B' will also be identi- 
cally illuminated and will stand out with the same relief from their 
respective backgrounds. This can only happen when A and B 
are equally illuminated. It affords a more sensitive ocular test 
of the equality of A and B than can be obtained by comparing 
them directly. The lights at the two ends of the bench are never 
of absolutely the same, and are sometimes of a widely differing, 
color. When a Welsbach light is tested against the Hefner lamp 
the field illuminated from the mantle burner is a clear blue color 
while the other is a yellow. The eye cannot determine with much 



126 GAS AND FUEL ANALYSIS 

accuracy when the yellow field and the blue one are illuminated 
to the same extent, but it can determine with greater accuracy 
when the yellow trapezoid A' stands out from its blue background 
with the same distinctness that the blue trapezoid B' stands out 
from its yellow background. The eye judges slight contrasts 
more accurately than large ones and therefore it is most sensitive 
when the photometer is almost at the neutral point. It is well 
to make an approximate setting for equality of A and B and then 
focus the attention on the contrast between the trapezoids and 
their respective backgrounds and complete the adjustment. 

13. The Flicker Photometer. — In the various forms of nicker 
photometer the light from each source is presented alternately 
and rapidly to the eye by means of revolving discs or prisms in 
the photometer box. When the intensity of light from the two 
sources is the same the nicker vanishes. No difficulty is experi- 
enced with lights of varying colors, but the photometer is fa- 
tiguing to the eye and its proper adjustment requires consid- 
erable skill. 

14. The Gas Meter. — The meters used in photometric work 
are of the same general type of wet meter as those described in 
§ 3 of Chapter VII for calorimetric work. They must be cali- 
brated with the same care and used with the same precautions. 
It is more convenient, however, to use a smaller meter which 
passes only 1/12 cu. ft. per revolution. When the gas is being 
burned at the rate of 5 cu. ft. an hour this meter will make exactly 
one revolution a minute. The dial of the meter is graduated into 
five parts with finer subdivisions. An observation of one minute 
will therefore give directly the uncorrected gas consumption in 
cubic feet per hour. Great care must be taken to see that the 
water of the meter is saturated with gas of the sort that is to be 
tested, for the " illuminants " of the gas are relatively soluble in 
water and a slight change in their percentage makes an appreci- 
able difference in the candle-power of the gas. 

15. The Photometer Bench and Its Equipment. — The preceding 
sections have discussed the various types of standard lights, 
burners and photometers which may be used. It is evident that 
wide latitude may be exercised in the choice of units and the 
method of assembling them to form a photometer bench. 

The details regarding the length of bar, type of standard light, 



CANDLE POWER OF ILEVMINATING GAS 



127 



form of test burner, kind "[^Z^™^^ 
for testing are in some cases con roUed by g ^ 

in some cases matters of arbitrary cuo h and tho 

ever, to trace two distmct hnes of mta ce ^^ ^ 

German. Of these the Engl sh is the old ^ and more 

more scientific. Modem methods of test g^^ u ig 
the grafting of German methods onto th g ^^ ^ 

ttZZZSZS*^ The photometric screen 




FlG# 34> __photometer bench. 

may be of cheaper t^*£^*S sticks fiS 
wooden construction with 1*^*^ £ America „ 60 
together. The bar most com monly q gas 

in. long. This n sufficxen ly accu candle . power longer 

flames are being tested. For lamps ot g 
bars are desirable. , j hown in Fig. 34. 

A photometer bench ^^^rand next to it the candle 
At the right hand end 1S shown th^m^ ^^ 

balances m po— ^hjhe fc£ .^ rf ^ c&ndles . At 
swinging arm so that it m^ " 



128 GAS AND FUEL ANALYSIS 

the left hand end is the Argand burner for the gas and between 
the two the bar itself with its screens and photometer. The 
piping for the gas is entirely below the table top but the pressure 
regulators and gages are shown above the table at the back. 

Precision photometers usually follow the German, or Reich- 
sanstalt, pattern in which the bar is built up of a rigid steel track 
on which the carriage of the photometric screen travels. The 
standard light and the test light are usually also mounted on a 
travelling carriage with provision for clamping them rigidly at 
any desired point of the bench. The length of the bench may 
thus be varied at will. 

16. Details of a Test. — The details of a test will of course vary 
with the equipment of the photometer bench and especially with 
the type of standard light employed. Directions for the use of 
these lights have been given in preceding sections. In the follow- 
ing paragraphs will be found general directions which are appli- 
cable to most forms of apparatus. 

The meter is to be examined to see that the water-level is 
correct and if necessary more water is to be added. In case 
the test is unusually important the meter should be calibrated 
against a tank of known volume. The tightness of connections 
between the meter and the burner is to be assured by turning the 
gas into the meter while keeping the stopcock on the burner 
closed. The meter hand should not show any perceptible motion 
in one minute. If there is a small leak allowance may be made 
for it in the calculations, but it is vastly better to have the whole 
apparatus tight. 

A clean chimney is to be placed on the Argand burner and the 
burner lighted. The pressure gage between the diaphragm 
governor and the burner should indicate about 1 in. of water pres- 
sure depending on the exact type of burner used. The consump- 
tion of gas is to be set so that the meter hand makes a revolution 
in approximately a minute and the light is then allowed to burn 
for at least fifteen minutes. If the meter has had much fresh 
water added to it, or if it was last used for a gas of a different 
quality than the one soon to be tested, or if the gas is being drawn 
from long lengths of pipes where the gas lies dead, a longer time 
than fifteen minutes must be allowed to elapse before commencing 
the test which must not be started until it is certain that the gas 



CANDLE POWER OF ILLUMINATING GAS 129 

burning is of representative quality and that it has not been 
changed by contact with the water of the meter. 

The final adjustment of the gas is made after taking into con- 
sideration the meter temperature and the barometric pressure. 
The desired rate of consumption being 5 cu. ft. measured under 
standard conditions, the correct apparent rate may be mentally 
calculated by adding to the 5 ft. 0.01 cu. ft. for each degree 
Fahrenheit shown by the meter thermometer above 60, and adding 
0.03 ft. for each 0.1 in. of mercury pressure below 30. For ex- 
ample, if the meter temperature is 80° F., and the barometric 
reading is 29.5 the uncorrected consumption of gas per hour should 
be 5.0+.20+.15 = 5.35. The gas is to be set to this desired flow 
with an error of less than 1/10 cu. ft. The stop-watch is started 
as the hand crosses the zero and stopped after one complete revo- 
lution. It should read between 59 and 61 seconds. After the gas 
has been satisfactorily adjusted and the standard lamp given a 
final adjustment the test may be commenced. 

The observer starts the stopwatch as the large hand of the 
meter passes the zero and steps quietly to the photometer avoid- 
ing sudden movements which would create drafts, and makes and 
records the first observation. Four more readings are made at 
intervals of about twenty seconds and then the photometric screen 
is reversed and five similar readings taken. If the lights flicker 
during an adjustment the observer must wait until the drafts have 
subsided before completing the observation. The series of ten 
observations usually requires about five minutes. At their con- 
clusion the operator steps back to the meter and stops the watch 
as the large hand of the meter again passes the zero. 

If a stopwatch is not available it is better to make the test 
during an even number of minutes rather than during the con- 
sumption of an even number of cubic feet of gas. If the observer 
holds the watch close to the meter and keeps his eyes on the watch 
till the second hand reaches the zero and then reads the position 
of the large meter hand, and follows the same precedure at the 
close of the test, the error will be well within the other necessary 
errors of the process. In case a stopwatch is available, it is more 
accurate to start the watch as the meter hand comes to its zero 
and to conclude the observation when the meter hand passes its 
zero, after the photometric observations have been completed. 



130 GAS AND FUEL ANALYSIS 

17. Illustration of Calculation. — The calculation which follows 
is for a test made on a 2500 mm. bench with a Hefner light as the 
standard. 

Date, Feb. 26. 

Source of Gas. Proportional Tank. Test 42. Experimental Gas Plant. 

Gas burned in London Argand. 

Standard Light — Hefner. 

Time Meter Reading 

Commencement of Test 10 : 16 : 00 a. m. 47.8 

End of test 10:21:00 50+24.6=74.6 



Duration 5 : 00 

Cubic feet gas uncorrected 26 . 8 

Cubic feet gas per hour uncorrected 5 . 36 

Meter Temperature 80° F. Error in meter less than 0. 1 per cent. 

Barometer 29.5 inches. Correction factor 0.973 

Cubic feet gas per hour uncorrected 5.36. Corrected 4.96 

Bar Readings 454, 456, 455, 462, 460 

460, 458, 460, 463, 464 Average 462. 

^ , , . r(2500-462) 2 XI 5.00 ,„ e 

Calculation (aro) 2 = ~Q X . Qfi = 17.6 candle-power. 

18. The Photometer Room. — The photometer bench must be 
placed in a room of reasonably constant temperature which is 
free from drafts and yet well ventilated. A room ventilated so 
that the carbon dioxide does not rise above ten parts in 10,000 
during a test is as much as can be expected in ordinary work. 
The carbon dioxide may rise to twenty parts without the air 
being more polluted than in an ordinary crowded street car in 
winter. The water vapor normally present in the air and that 
given off by the flames and the respiration of persons in the 
photometer room exerts an even greater influence on flames than 
the carbon dioxide but since its accurate determination is difficult, 
the carbon dioxide is usually taken as the measure of contamina- 
tion of the air. 

The committee on Photometry of the American Gas Institute 1 
have published some curves showing the variation of certain 
flames with increased carbon dioxide when compared with an 
incandescent electric lamp. The humidity of the air varied so 

l Proc. Am. Gas. Inst., 11, 480 (1907). 



CANDLE POWER OF ILLUMINATING GAS 131 

much from day to day that a comparison of one day's work with 
another could not be made and the following figures from their 
curves must be taken as merely illustrative of the large errors 
that may arise. 

COMPARISON OF PENTANE LAMP WITH GAS FLAME 

Parts C0 2 in 10,000 10.0 20.0 

Per cent, loss of candle-power gas flame 4.0 20.0 

Per cent, loss of candle-power pentane 7.5 31.0 

COMPARISON OF PENTANE LAMP WITH CANDLES 

Parts C0 2 in 10,000 • 10.0 20.0 

Per cent, loss of candle power, candles 19.0 27. 

Per cent, loss of candle power pentane 13.0 16. 5 

It is therefore evident that the usual assumption that the 
standard light and the test light are equally affected by atmos- 
pheric conditions, is erroneous and that care should be taken to 
have the test made under as favorable atmospheric conditions 
as possible. 

19. Jet Photometers. — There are two main types of jet pho- 
tometers. In one type, gas passes through a pressure regu- 
lator and issues at constant pressure through a small round 
orifice where it burns in a jet whose height as read on the glass 
chimney is assumed to give candle power directly. In the other 
type of jet photometer the gas flame is kept at a constant height 
and the pressure required to force the gas through the burner 
opening is measured as an indication of candle power. No type 
of jet photometer can be relied on to do more than give approxi- 
mate determinations. They should be calibrated frequently 
against a bar photometer. 

20. Accuracy of Photometric Work. — When it is recollected 
that the Reichsanstalt certifies a Hefner lamp as correct if it is 
within 2 per cent, of their standard, and that the absolute value 
of the pentane lamp may vary as much as 25 per cent. 1 in the 
course of a year on account of changing atmospheric conditions 
and further that the human eye is a very inaccurate scientific 
instrument, a greater accuracy than half a candle can hardly be 

1 J. B. Klumpp, Proc. Am. Gas Light Assoc, 1905. Appendix. 



132 GAS AND FUEL ANALYSIS 

expected with illuminating gas tested under ordinary conditions. 
Much larger errors may creep in unless care is taken. 

The determination of candle power has largely lost its signifi- 
cance as a criterion for municipal gas supplies, since from 75 
to 90 per cent, of the gas sold is used for heating, or in Welsbach 
burners, where the heat value is a much better criterion. The 
international Photometric Commission in 1911 passes the follow- 
ing resolution. 1 

" The International Photometric Commission is, after consideration of the 
present uses of illuminating gas, of the opinion that the illuminating value 
of gas flame has lost its significance and that the determination of the heat- 
ing value should replace the determination of candle power as the most 
important criterion of its value." 

1 Jour, fur Gasbel, 1911, 1002. 



CHAPTER IX 
ESTIMATION OF SUSPENDED PARTICLES IN GAS 

1. Introduction. — The estimation of particles held in suspen- 
sion in gases is daily becoming of greater importance on account 
of legal restrictions on pollution of the air and on account of 
insistence on closer control of industrial operations by manu- 
facturers. The problem is one of great difficulty and is usually 
susceptible of only approximate solution. Not only is it difficult 
to obtain the suspended solids present in a flue at a given point 
and time, but it is difficult to determine whether the solids thus 
determined were normal in amount or whether they were, for 
instance, low because of the deposition of an unusually large pro- 
portion prior to the point of sampling on account of slower veloc- 
ity of gas in the main, or because of lower temperature or for some 
other reason. 

2. The Distribution of Particles in the Cross-section of a 
Straight Main. — If the main is horizontal it is evident that there 
will tend to be a stratification of the particles, the large and heavy 
particles separating faster than the fine and light. This tendency 
to settle is, however, resisted by the whirling motion which 
gases traversing flues frequently possess and which is frequently 
caused by the inequalities in pressure produced by bends in the 
pipe. The velocity of gas in a straight main at ordinary working 
speeds is greatest at the center and least at the walls. The 
shape of the wave front varies with the speed of the gas, high 
velocities accentuating the difference. Solid particles are pushed 
gradually out of the zone of high velocity into one of lower 
velocity in the same way that a piece of wood in a river is grad- 
ually pushed to the still waters along the bank. This action 
takes place in a vertical as well as a horizontal main. 

The solids contained in a gas at the point of greatest velocity 
will therefore be the least in amount, the smallest in size, and the 
lowest in specific gravity. The quantity of particles, their size 
and specific gravity will all increase in the regions where velocity 

133 



134 GAS AND FUEL ANALYSIS 

is least. In a normal round main this point of greatest velocity 
is the center where will be found the fewest and lightest solid 
particles. Their quantity and magnitude increase in successive 
rings to the circumference. If the velocity of the gas is decreased 
until the main is also acting as a settling chamber there will be 
little difference in the velocity throughout the cross-section and 
the region near the top of the main will contain the fewest solid 
particles. 

This uneven distribution of suspended particles in a gas 
stream may take place very rapidly as was shown by the author 1 
some years ago in an attempt to determine the amount of sus- 
pended tar in unpurified illuminating gas. A 14-in. main con- 
taining unpurified illuminating gas was tapped on its horizontal 
axis at a point a few feet beyond the exhauster and two sampling 
tubes inserted, one extending to the middle of the main and the 
other projecting through the wall only about an inch. Four 
tests were made and in each case the suspended tar caught in the 
sampling tube near the edge of the main was more than twice as 
great as that found in the tube projecting to the center. 

3. Mean Velocity in the Cross-section of a Gas Main. — Threl- 
fall 2 has shown that it is necessary to investigate the distribution 
of velocity for each individual case as it arises, but that in general 
the radius of the circle of mean velocity is about 0.775 of the ra- 
dius of the pipe. In one case it was as high as 0.9 of the radius but 
in no case did it sink to 0.69 which is the figure quoted for water 
flowing through a long and smooth pipe. The radius of mean 
velocity did not change with varying speed of gas flowing through 
the pipe within the ranges of 600 ft. and 3600 ft. per minute, 
which marked the limit of the experiments. Threlfall's experi- 
ments were on pipes varying from 6 to 36 in. in diameter. 

4. Influence of Bends in a Main. — If gas flowing through a 
straight main comes to a bend there will be a change in the rela- 
tive velocities of the particles of the gas throughout the cross- 
section. The kinetic energy of a body is represented by the 
expression l/2mv 2 where m represents the mass of a body and v its 
velocity. It is evident therefore that the particles with the 
greatest mass and the greatest velocity will be projected beyond 

1 Proc. Mich. Gas. Ass., 1906. 
2 Proc. Inst Mech. Eng., 1904, 1, 245. 



ESTIMATION OF SUSPENDED PARTICLES IN GAS 135 

their companions. The point of maximum velocity will shift 
from the center to a point nearer the opposing wall and will then 
slowly return to its normal position with a spiral movement. 
Solid particles on account of their greater mass may strike the 
opposing wall and if they or the wall are sticky may adhere there 
and build up deposits. 

It will be evident, from what has preceded, that it will not be 
possible to find a single point in a gas main from which it is pos- 
sible to draw a fair sample of gas for the determination of sus- 
pended solids. If a sample can only be taken at a single point, 
the termination of the sampling tube should be at about the point 
of mean velocity, as explained in the preceding section. In im- 
portant tests it is advisable to draw a number of samples from 
various points in the cross-section of the main. A tube with nu- 
merous perforations along its length is useless for this work. Sep- 
arate tubes should be used each with its own filter and aspi- 
rator as explained in Chapter I. 

5. Velocity of Gas in a Sampling Tube.— The rate of flow 
through the sampling tube has a ma- 
terial effect on the accuracy of sam- 
pling as has also the inclination of the 

sampling tube to the gas stream. It _> 

is evident that if a sampling tube is 

inserted at A of Fig. 35 at right angles 
to the flow of gas, even assuming that 
the solid particles are uniformly dis- 
tributed, the result will be incorrect FlG 35 ._ Diagram show . 
for the heavy particles will tend to be i ng me thod of inserting sam- 
carried past the open end of the tube pling tube in gas main, 
and not drawn into it. The suspended 

solids will be reported low even if the speed of gas within the sam- 
pling tube is as high or even higher than that in the main. If, on 
the other hand, the opening of the sampling tube faces the 
approaching stream of solid particles as at B, on the same assump- 
tion of uniform distribution of particles, the result may be cor- 
rect, or it may be high or low. If the speed of the gas in the sam- 
pling tube is the same as that in the main the result should theo- 
retically be correct. The whole column of gas opposite the open- 
ing of the tube should enter without distortion. If, however, the 



136 GAS AND FUEL ANALYSIS 

velocity in the sampling tube is lower than that in the main 
the column of gas approaching the opening will be disturbed and 
part of it will be forced aside. 'The solid particles will on account 
of their momentum not be pushed aside so readily and will there- 
fore enter the tube in unduly great amount, giving a high result. 
If the velocity of the gas in the sampling tube is greater than that 
in the main there will again be a disturbance in the approaching 
column of gas. A column of gas larger than the opening of the 
tube will be sucked in, but the solid particles in the outer shell 
of gas thus sucked in will not be diverted from their course and 
will pass by the opening of the tube, giving a low result. Brady 1 
states that in sampling blast-furnace gas an error of more than 
44 per cent, was caused when the sampling speed was dropped to 
half that in the main. It is thus evident that the speed with 
which gas enters the sampling tube must be carefully controlled. 
The velocity of the gas must however be reduced before it 
passes through the filtering medium or the finely divided particles 
will not be taken out. The usual sampling tube has therefore a 
relatively small aperture. Care must be taken that the aperture 
is not so small that it will become clogged, which readily happens 
when tarry matters are present. Each case must be studied 
independently. 

6. The Filtering Medium. — Where conditions permit, filter 
paper discs or shells make satisfactory filtering media. The 
Brady gas filter for dust in blast-furnace gas is described in the 
article referred to in the preceding section. A filter using a disc 
of filter paper as developed by Mr. W. S. Blauvelt 2 of the Semet- 
Solvay Company has been used by the author with good results. 

When large amounts of tar are present a weighed tube filled 
with a fibrous material may with advantage be inserted ahead of 
the filter paper. The filtering materials to be inserted in the sam- 
pling tube will vary with conditions. If the temperature is high, 
sand or ignited asbestos is suitable. Ignited asbestos is usually to 
be preferred since on account of its fibrous nature it makes a more 
efficient and a lighter filter. This last consideration is of impor- 
tance since the suspended solids collected frequently weigh only 
a few milligrams and it conduces to accuracy to have the increase 

1 Jour. Ind and Eng. Chem., 3, 662 (1911). 
2 Proc. Am. Gas. Inst., 4, 795 (1909). 



ESTIMATION OF SUSPENDED PARTICLES IN GAS 137 

in weight of the filter relative to its initial weight as large as may 
be. The tubes may be of glass, porcelain or quartz protected if 
desirable by an iron j acket. The tubes after filling and before use 
should be placed in an air bath heated to the temperature to which 
they are to be exposed later and dry air should be drawn through 
them until they are constant in weight. They should then be 
cooled in dry air, weighed, carefully stoppered and if possible 
kept in a dessicator until used. The asbestos for this purpose 
should not be soft enough to pack readily and choke the tube. 
The fine washed asbestos used for analytical work is not so good for 
this purpose as a cruder sort. Sometimes when much tar is 
present it is advantageous to procure the crude asbestos rock and 
merely crush it coarsely in an iron mortar. 

7. Estimation of Suspended Tar and Water. — The amount 
of suspended matters caught by a filter paper may be estimated 
either by color or, if sufficient in amount, may be determined by 
weight. A second weight after drying at 105° C. for an hour will 
give by difference the moisture and other volatile matter, while 
the weight after ignition will give the mineral matter, correction 
being made if necessary for the change in composition due to 
ignition. 

Where asbestos filters have been used a smiliar procedure may 
be followed provided the asbestos has been ignited before use. 
In drying the tube however it is not sufficient to heat it externally. 
Dry air must be drawn through until it comes to constant weight. 
The water will be driven off and also approximately 25 per cent, 
of the weight of the tar. The non-volatile tar remaining may 
afterward be extracted with chloroform or carbon bisulphide, 
and this figure increased by one-third will give a rough estimate 
of the amount of tar present. It is not possible to determine 
accurately the amounts of water and suspended tar since it is not 
feasible to determine how much of the material volatilized is tar 
and how much is water. 

8. Electrical Precipitation of Suspended Particles. — Where 
the expense warrants the installation of the process, the method of 
electrical precipitation as developed on the large scale so success- 
fully by Cottrell 1 may be applied. The equipment consists of a 
small step-up autotransformer capable of giving 15,000-30,000 

1 Jour. Ind. and Eng. Chem., 3, 542, (1911). 



138 GAS AND FUEL ANALYSIS 

volts, a rotating switch to rectify this high-tension alternating 
current and a precipitating vessel which may be made of an iron 
pipe with an insulated electrode in the center An exhauster 
for aspirating the gas and a meter for measuring it must also 
be provided. This apparatus will quantitatively precipitate all 
suspended solid and liquid bodies including tar and operates on 
such large amounts that the precipitated materials can readily be 
examined. 



CHAPTER X 
CHIMNEY GASES 

1. Introduction. — A knowledge of the chemical composition 
of the gases escaping from a chimney aids much in controlling 
the efficiency of the furnace. It makes very little difference 
whether the fuel is burned to raise steam or to melt steel and it is 
of equally small importance whether the fuel burned be solid or 
liquid. The only assumption is that it is desirable to burn the 
fuel as completely as possible without the introduction of any 
unnecessary excess of air. When gaseous fuels are burned the 
same general principles apply but there is somewhat greater 
complication in calculation. This chapter therefore limits itself 
to a study of the gases arising from complete combustion of 
solid or liquid fuels. Let us see how much light a knowledge of 
the composition of the gas can throw on the operation of the 
furnace. 

2. Formation of Carbon Dioxide. — Air is composed of 
practically 21 volumes of oxygen and 79 volumes of nitrogen and 
other inert gases. When oxygen unites with carbon there is 
formed carbon dioxide which is stable unless it comes into inti- 
mate contact with carbon or other reducing agent at a high tem- 
perature. Chemically the result is expressed as follows: 

c+o 2 =co 2 . 

The expression means not only that carbon dioxide is formed 
by the union of carbon and oxygen, but also indicates that one 
volume of carbon dioxide is formed from one volume of oxygen and 
that the volume of the smoke gases after cooling is the same as that 
of the air which was used. This follows from the law of Gay 
Lussac which states that a molecule of one gas occupies the same 
volume as that of any other gas under like conditions. The 
simplicity of this volume relation makes it extremely desirable 
to work with volumes instead of weights in problems where gases 
are involved. 

139 



140 GAS AND FUEL ANALYSIS 

Since one volume of oxygen forms one volume of carbon dioxide 
it follows that the theoretical best composition of the chimney 
gases from the combustion of carbon would be 21 per cent. C0 2 
and 79 per cent. N 2 . This is unattainable in practice because the 
strong reducing action of the glowing carbon on the carbon 
dioxide will cause formation of carbon monoxide (CO) which will 
not be again oxidized unless it is brought in contact with free 
oxygen while still at a high temperature. An excess of oxygen is 
in practice necessary to ensure this. It follows from the fact that 
the volume of the carbon dioxide is the same as that of the oxygen 
which formed it, that all chimney gases resulting from the combus- 
tion of pure carbon to carbon dioxide will contain 21 per cent, of 
CO2+O2 and 79 per cent, of N 2 . 

3. Effect of Hydrogen of Coal on Composition of Chimney 
Gases. — The simple relation stated in the preceding section only 
holds where carbon is the only fuel burned, a condition which is 
quite closely fulfilled with a coke fire and approximately ful- 
filled when anthracite coal is the fuel. When fuels contain not- 
able percentages of hydrogen as does bituminous coal, and to a 
greater extent petroleum and most gaseous fuels, part of the 
oxygen of the air burns to water which escapes from the furnace 
as steam. When the gas is sampled for analysis part of this steam 
may condense. When the gas sample is stored over water it 
becomes fully saturated with water vapor so that its volume is in- 
dependent of the amount of steam which it contained in the chim- 
ney and the result is the same as if the steam formed in combustion 
had all condensed and the gas had later become saturated with 
water vapor as happens, for instance, in the gas analysis appa- 
ratus. This is the assumption which is made in discussing 
combustion. 

If, then, part of the oxygen of the air combines with hydrogen 
of the fuel to form steam which condenses to a liquid while the 
nitrogen associated with this oxygen remains as a gas, it is apparent 
that the percentage of nitrogen in the chimney gas must be more 
than the 79 per cent, present in the air. The extent of the change 
of volume may be readily calculated. Assume that an analysis 
shows 81 per cent. N 2 . 100 cu. ft. of air contained 79 cu. ft. of 
nitrogen, which is now 81 per cent, of the chimney gas, therefore 

79 
the volume of the gas is ~-^ = 0.975 or 97.5 per cent, of the initial 



CHIMNEY GASES 141 

volume of air measured under the same condition of temperature 
and pressure. It follows that 2.5 of the 21 volumes of oxygen 
in 100 air have combined with hydrogen to form water. 

The volume of the water formed, so long as it remains in the 
vapor form, will be twice that of the oxygen from which it was 
formed as shown by the equation 

2H 2 + 2 = 2H 2 0. 

The hydrogen in this case is contained in the coal and is considered 
as a solid just as the carbon is. In the case of gaseous fuels the 
problem is a little more complicated and is treated under Pro- 
ducer Gas. 

4. Carbon Monoxide and Products of Incomplete Combus- 
tion. — The presence of carbon monoxide, hydrogen or hydro- 
carbons is a sign of incomplete combustion and represents 
loss of heat which would have been liberated in the furnace had 
combustion been complete. 

Heating value 1 lb. C to C0 2 14,600 B.t.u. 

1 lb. C to CO 4,450 B.t.u. 

Since carbon burning to CO only evolves 30 per cent, of the heat 
obtainable by complete combustion it is evidently uneconomical 
to allow more than small amounts of this gas to appear in chimney 
gases. 

It is frequently stated that carbon monoxide is formed when 
carbon burns with an insufficient supply of air. This is only a 
partial truth for with a bed of coals at a dull red heat it is difficult 
to form carbon monoxide no matter how much the air supply is 
limited. If the free oxygen in the chimney gases is below 3 
per cent, it will be entirely normal to find products of incomplete 
combustion. The presence of carbon monoxide and other in- 
completely burned gases is abnormal when associated with much 
more than 3 per cent, free oxygen. It indicates either a faulty 
design of the furnace or carelessness on the part of the fireman. 
Furnaces intended for coal high in volatile matter must have 
roomy combustion chambers so that the streams of gas given off 
by the coal may have time to mix with air and burn before they 
become chilled by contact with cold surfaces. Furnaces designed 
for anthracite coal do not have such large combustion chambers 
and hence do not give good results with bituminous coal. 



142 GAS AND FUEL ANALYSIS 

As mentioned in Chapter III, the estimation of carbon monoxide 
presents some difficulties and the careless analyst may readily 
report a fraction of a per cent, of carbon monoxide when none is 
there. On the other hand, the natural tendency is to fail to find 
hydrogen when it is present in only small amounts. 

The presence of soot in chimney gases is not necessarily an in- 
dication that measureable amounts of unburned gases are present 
for the particles of tar and carbon formed by the destructive 
distillation of the coal burn much more slowly than do the 
gases and also have higher ignition temperatures and so are more 
likely to escape combustion. 

5. Volume of Air and of Chimney Gases. — The volume of the 
air used in combustion per pound of carbon and the volume of the 
chimney gases may be calculated from the gas analysis. The 
method is based on the assumption that the nitrogen of the air 
passes through the furnace unchanged in volume, and that all of 
the nitrogen of the chimney gases is derived from the air. This 
assumption is practically correct, the small amount of nitrogen 
derived from the coal introducing only a negligible error. 

It is necessary also to have some factor to connect the weight 
of carbon burned with the volume of the chimney gases. One 
pound of carbon burning to CO2 requires 32.1 cu. ft. of oxygen 
measured wet at 60° F. and 30 in. barometric pressure and 
yields 32.1 cu. ft. carbon dioxide. 

Let us assume the following gas analysis : 

C0 2 8.5 per cent. 

2 9.8 per cent. 

N 2 81.7 per cent. 

It was shown in § 3 that the increase in the percentage of the 

nitrogen over 79 was due to the condensation of steam formed by 

the union of hydrogen of the coal with oxygen of the air. The 

volume of these gases referred to 100 of air may be obtained by 

79 
multiplying them by the factor «r^ = 0.966. 

8.5X0.966= 8.2C0 2 
9.8X0.966= 9.5 2 
81.7X0.966 = 78.8 N 2 
96.5 
2 which has disappeared as steam 3.5 forming 7.0 steam. 

100.0 



CHIMNEY GASES 143 

The volume of air used per pound of carbon may now be ob- 
tained. 

To burn 1 lb. carbon =32. 1 cu. ft. 2 forming 32. 1 cu. ft. C0 2 

32.1X9.5 
Oxygen in excess g-~ =37.2 

3 2.1X3.5 
Oxygen forming steam ^— ~ =13.7 

Total oxygen per pound carbon, 83 . cu. ft. 

79 
Accompanied by 2i X 83.0 =312.0 cu. ft. N 2 

Corresponding to 395.0 cu. ft. air. 

The excess of air may be determined from the ratio 
Oxygen used 32 . 1 +37 . 2-f- 13 . 7 _ 83 . 
Oxygen required" 32.1+13.7 ~45.8 

The volume of the chimney gases is obtained directly from the 
above, it being remembered that the volume of the CO2 is the 
same as that of the O2 forming it and that the volume of the steam 
(assumed to be cooled to standard temperature without condensa- 
tion) is twice the volume of the oxygen forming it. 

Volume of chimney gases from 1 lb. carbon in the above 
example : 

C0 2 , 32.1 cu. ft. 

H 2 vapor 2X13.7 27.4 cu. ft. 

2 37.2 cu. ft. 

N 2 312.0 cu. ft. 

Total chimney gases 408.7 cu. ft. 

6. Loss of Heat in Chimney Gases. — The heat carried away 
by these gases may be determined by multiplying their volume by 
the rise in temperature* and by their specific heat. It was first 
shown in 1883 by Mallard and LeChatelier that the specific heats 
of gases are not constant but increase with rising temperature. 
Engineers have been slow to adopt these variable specific heats 
but there can be no question as to their general correctness. The 
mean specific heats expressed in British thermal units per cubic 
foot and per pound at constant pressure have been calculated by 
the author from the most recent data of Holborn and Henning 1 

1 Annalen der Physik, 23, 809 (1907). 



144 GAS AND FUEL ANALYSIS 

and are given in Tables V and VI of the Appendix. It will be 
noted that the specific heats of oxygen, nitrogen and all permanent 
gases are the same per cubic foot, an agreement which holds true 
only for specific heats by volume and not for those for which the 
unit basis is weight. 

The loss of heat per pound of carbon in the particular case 
given above will be calculated as follows, a temperature of 600° 
F. for the escaping gases being assumed : 

Temperature through which gases are heated 600 — 60 = 540. 
Use mean specific heats from Table V corresponding to 600° F. 

Heat lost in C0 2 , 32.1X0.0253X540 = 439 B.t.u. 

Heat lost in steam , 27 . 4 X . 022 1 X 540 = 328 

Heat lost in oxygen, 37.2 \ 349 . 2x0 .0177x540 =3340 B.t.u. 

Heat lost in nitrogen, 312 J 

4107 

It is necessary to know the percentage of carbon in the coal 
before this loss of heat per pound carbon can be calculated to 
the desired basis of loss per pound of coal. 
The loss of heat per pound of dry coal = 

Loss per pound carbon X per cent, carbon in dry coal 
~100 

Moisture present in the coal when placed on the fire will be 
vaporized, and, in case combustion is complete, will escape from 
the stack as steam. It is immaterial whether or not it underwent 
decomposition in the fire, only the initial and final states being 
important. The amount of water thus vaporized calculated 
from the analysis of the coal is reported in pounds and is most 
conveniently kept in that form throughout the calculation. The 
mean specific heats by weight at constant pressure are given in 
Table VI of the Appendix. Moisture present in the air intro- 
duced into the firebox will be heated from room temperature to 
that of the escaping gases. Its amount may be determined from 
observations with a wet and dry bulb thermometer from which the 
percentage humidity may be calculated as described in § 14 of 
Chapter VII. The volume of water vapor per cubic foot of air 
for various temperatures is given in Table VII of the Appendix. 

There is also steam in the stack gases which is derived from 
the union of the hydrogen and oxygen of the coal with each 
other. It is sufficiently accurate to assume that all of the oxy- 



CHIMNEY GASES 145 

gen of the coal unites with the hydrogen of the coal to form water, 
that the excess or available hydrogen unites with the oxygen of 
the air to form water and that all of the carbon of the coal 
unites with the oxygen of the air to form carbon dioxide. The 
volume of steam due to this union of the hydrogen and oxygen 
of the coal with each other can only be accurately calculated from 
an ultimate analysis. Fortunately its amount is small and fairly 
constant for a given type of coal. The weight of water so formed, 
sometimes called " combined water," may be taken as: 

2.5 per cent for anthracite coals. 
6.0 per cent for Eastern bituminous coals. 
10.0 per cent for bituminous coals of the Western or Illinois type. 

These figures may for this purpose be added to the percentage 
of moisture in the coal. 

There are also changes in the ash of the coal which may in- 
volve absorption of oxygen or liberation of SO2 or CO2 but they 
are negligible in a calculation of this sort. 

PROBLEM ILLUSTRATING CALCULATION OF LOSS OF HEAT IN 
CHIMNEY GASES 



Data Coal as charged 



Average composition of 
chimney gases 



Moisture 9.3 per cent. 

Volatile matter . . 31.7 C0 2 9.6 per cent. 

Fixed carbon 53.7 2 9.0 

Ash 5.3 N 2 81.4 

100.0 100.0 

B.t.u. per lb. . . 12,456 Temp, escaping gases. . 720° F. 

Per cent, total carbon. . . 71 .6 Temp, inlet air 70° F. 

Relative humidity 75 per cent. 

VOLUME CHIMNEY GASES REFERRED TO 100 VOLUMES OF 
DRY AIR ENTERING FURNACE 

79 
Factor = g^= 0.97 

9.6X0.97= 9.3 C0 2 
9.0X0.97= 8.7 2 
81.4X0.97=79^0 N 2 
97.0 
Oxygen which has disappeared to form H 2 3.0 forming 6.0 H 2 
vapor. 100.0 

10 



146 GAS AND FUEL ANALYSIS 

Volume chimney gases from 1 lb. carbon. 

32 1 
1 lb. carbon produces 32.1 cu. ft. C0 2 . Factor =3.45 

9.3X3.45= 32.1 cu. ft. C0 2 

6.0X3.45= 20.7 cu. ft. H 2 vapor 

8.7X3.45= 30.0 cu. ft. 2 

79.0X3.45=272.2 cu. ft. N 2 



Volume air required for combustion 100X3.45=345 cu. ft. 
Moisture in air for combustion: 



75 per cent, of saturation at 70° =0.75X0.026 =0.019 cu. ft. per 

cubic foot air. 
345X0.019 = 6.56 cu. ft. H 2 vapor in air for 1 lb. carbon. 



Gases heated from 70° -720° = 650° F. 

LossinC0 2 =32.1X650X0.0253 =529 

LossinH 2 =20.7+6.6=27.3X650X0.0221 = 392 

Loss in 2 + N 2 =30. 0+272. 2 =302. 2X650X0. 0177 =3440 

B.t.u. lost in gases per lb. carbon burned =4361 

B.t.u. lost in gases per lb. coal burned 4361X0.0716 =3122 

Moisture in coal 9.3 per cent =0.093 lbs. per lb. coal. 

Combined water in coal 6.0 per cent =0.060 lbs. per lb. coal. 

Total water with coal =0.153 lbs. per lb. coal. 



Heat absorbed in converting 1 lb. water 

to vapor at 70° F. =1067. B.t.u. 
Heat absorbed in converting 0. 153 lbs. 

water to vapor at 70° F. =0.153 

X1067. 
Heat absorbed in raising 0.153 lbs. 

water vapor from 70° — 720° = 

0.153X650. X 0.4673 
Total heat lost in water with coal 
Heat lost in gases per lb. coal 
Heat lost in water per lb. coal 
Total heat lost per lb. coal burned 

3331 
Per cent, heat lost = ^455 =26.7 per cent 



163. 


B.t.u, 


46. 


B.t.u. 


209. 


B.t.u. 


3122. 


B.t.u, 


209. 


B.t.u. 


3331. 


B.t.u. 



CHIMNEY GASES 147 

7. Interpretation of Analysis of Chimney Gases. — The con- 
clusions indicated in the preceding paragraphs may be summar- 
ized as follows: 

Carbon Dioxide. — The higher the percentage of C0 2 in chimney 
gases without the presence of CO or hydrocarbons, the more 
efficient is the furnace. When the fuel is coke or anthracite coal 
the sum of the percentages of carbon dioxide and oxygen should be 
between 20.5 and 20.8. If the fuel is bituminous coal the sum of 
the carbon dioxide and oxygen will drop to 19 per cent, and if the 
fuel is oil or gas the figure will be still smaller. In ordinary prac- 
tice the percentage of carbon dioxide should be as large as the 
oxygen, and with well-equipped and operated plants the pro- 
portion of CO2 to 2 should be as high as 2 to 1. With liquid or 
gaseous fuels the proportion of C0 2 will be still higher. 

The C0 2 as reported includes a small amount of S0 2 from the 
sulphur of the coal, which does not usually amount to more than 
a few hundredths of a per cent. 

Oxygen. — When solid fuel is burned on an ordinary grate it is 
necessary to have an excess of air to insure complete combustion. 
This excess should be kept as small as possible. 

Carbon Monoxide and Products of Incomplete Combustion. — 
These products should be entirely absent from chimney gases. 
Their presence indicates waste of fuel. Unless the analytical 
work is carefully done as much as 0.2 per cent. CO may readily be 
reported through error. 

Nitrogen. — Nitrogen is present in air to the extent of 79 per 
cent, by volume and will be present in at least that percentage in 
chimney gases. With bituminous coal the percentage will rise 
to 81 per cent, and with oil or gaseous fuel the percentage will 
be higher. The percentage of nitrogen can only fall below 79 
per cent, through the introduction of some gas which makes the 
total volume of the chimney gases greater than that of the air from 
which they were derived. The formation of carbon monoxide 
will affect this result since it occupies twice as much space as 
the oxygen from which it was derived. The amount of CO in 
chimney gases is, however, too small to exert any appreciable 
influence of this sort. 

Loss of Heat in Chimney Gases. — The loss of heat will depend 
on the temperature and volume of the gases. The volume of the 



148 GAS AND FUEL ANALYSIS 

gas is in general indicated by the relative percentage of carbon 
dioxide and oxygen. The higher the per cent, of oxygen and the 
lower the per cent, of carbon dioxide the greater is the loss of heat. 
The loss will vary in steam-boiler practice between 15 and 45 
per cent. With smelting furnaces where the gases escape at 
high temperatures the loss may be much higher. 



CHAPTER XI 
PRODUCER GAS 

1. Formation of Producer Gas. — Producer gas is formed 
whenever air is brought into contact with fuel under such con- 
ditions that carbon monoxide is an important constituent of the 
products resulting from their combination. The formation of pro- 
ducer gas is frequently said to be due to incomplete combustion, 
but the statement is only a half truth, for a limited quantity of 
air supplied to a fire will not necessarily produce carbon monox- 
ide. The primary product formed when carbon burns in air 
is carbon dioxide, the equation being written 

c+o 2 =co 2 

If this carbon dioxide comes into intimate contact with glowing 
carbon, it unites with more carbon and carbon monoxide is 
formed according to the equation 

C0 2 +C<=±2CO. 

These two reactions are frequently combined into one and the 
typical reaction of the gas producer is usually written 

2C + 2 = 2CO. 

This equation shows that one volume of oxygen is converted 
into two of carbon monoxide. The composition of the resulting 
gas may be shown as follows : 

• = J 21 °2 =42CO = 34.7 per cent. CO. 
air- j 79N2 = 79N2 =65<3 per cent> N2> 

When steam is introduced in the bottom of the producer the 
reaction desired is: 

C + H 2 = CO + H 2 . 
149 



150 



GAS AND FUEL ANALYSIS 



If the temperature of the producer is low, this reaction may 
proceed in part as follows: 

C + 2H 2 = C0 2 + 2H 2 . 

If bituminous coal is placed in the producer there will also be 
products of destructive distillation including hydrocarbons both 
saturated and unsaturated, hydrogen and carbon monoxide. 

The largest single constituent of producer gas is nitrogen, which 
will not often fall below 50 per cent. Carbon monoxide and 
hydrogen rank next in percentage. The hydrocarbons are 
practically always under 5 and are usually less than 3 per 
cent. Carbon dioxide should be low. It is, however, frequently 
as high as 10 per cent. 

The following are some typical analyses of producer gas. 1 

TYPICAL ANALYSES OF UP-DRAFT PRESSURE-PRODUCER GAS 



(Pei 


• cent, by volume) 








From 
Bituminous Coal 


From 
Lignite 


From 
Peat 


Carbon dioxide (C0 2 ) 

Oxvgen (O2) 


9.84 

.04 

.18 

18.28 

12.90 

3.12 

55.64 


10.55 
0.16 
0.17 

18.72 

13.74 
3.44 

53.22 


12.40 
0.00 


Ethylene (C 2 H 4 ) 


0.04 


Carbon Monoxide (CO) 

Hydrogen (H 2 ) 

Methane (CH 4 ) 


21.00 

18.50 

2.20 


Nitrogen (N 2 ) 


45.50 



TYPICAL ANALYSES OF DOWN-DRAFT PRODUCER GAS 
(Per cent, by volume) 



From 


From 


From 


Bituminous Coal 


Lignite 


Peat 


6.22 


11.87 


10.94 


0.13 


0.01 


0.41 


0.01 


0.00 


0.06 


21.05 


16.01 


16.91 


12.01 


14.76 


10.19 


0.49 


0.98 


0.66 


60.09 


56.37 


60.83 



Carbon dioxide (C0 2 ) . . 

Oxygen (0 2 ) 

Ethylene (C 2 H 4 ) 

Carbon monoxide (CO) 

Hydrogen (H 2 ) 

Methane (CH 4 ) 

Nitrogen (N 2 ) 



1 From Bulletin 13, U. S. Bureau of Mines. "Resume" of Producer-Gas 
Investigations by R. H. Fernald and C. D. Smith. 



PRODUCER GAS 151 

2. Sampling Producer Gas. — The quality of gas yielded 
by a given producer may change quickly. Soon after a charge 
of bituminous coal has been added, the amount of volatile tarry 
vapors and of gaseous hydrocarbons in the gas increases. Within 
a half hour the larger part of the volatile matters may have dis- 
tilled off leaving the gas almost free from hydrocarbons and from 
tar vapors. Rapid changes will also be noted after poking the 
fire. 

An average sample of producer gas may be obtained only 
by extending the sampling over a long period, as directed in 
Chapter I. There will be especial difficulty in determining the 
quantity and heat value of the suspended tarry particles. Yet 
these values must be ascertained if the heat value of the crude 
gas is to be determined accurately. The method of collecting 
the tar particles on filter papers, given in Chapter IX, may be 
followed and the weight of tar per cubic foot of gas thus obtained. 
The papers and tar may then be burned in a bomb calorimeter 
and after deduction of the heat due to the known amount of 
filter paper, the heating value of the tar may be obtained. This 
determination is not often made, as it is difficult to carry it out 
accurately. However, it is not possible to find the true heat 
balance on a furnace fired with crude producer gas, especially if 
from a bituminous producer, unless such a determination is made. 

Ordinarily the determination of tar and suspended particles 
is neglected and the sampling then is to be conducted as described 
in Chapter I. 

3. Analysis of Producer Gas. — The constituents to be 
determined in producer gas are carbon dioxide, unsaturated 
hydrocarbons, oxygen, carbon monoxide, hydrogen and methane. 
The methods are given in Chapters II, III and IV. No difficulty 
will be experienced except with hydrogen and methane. The 
percentage of these gases, except in water gas, is usually so small 
that a sample after removal of the absorbable constituents is no 
longer explosive when mixed with air. It should be emphasized 
that failure to obtain an explosion does not mean the absence 
of hydrogen and methane but merely that they are present in 
less than explosive amounts. Explosion may be brought about 
by addition of a known volume of pure hydrogen to form an 
explosive mixture but it is usually simpler to use a method which 



152 GAS AND FUEL ANALYSIS 

does not involve explosion. Combustion with a hot platinum 
spiral as in the Dennis and Hopkins method ( § 9 of Chapter IV) 
or with copper oxide as in the Jaeger method (§ 11 of Chapter 
IV) affords a satisfactory method for determination of these 
constituents. 

4. Interpretation of Analysis. — The important constituents 
are carbon dioxide and carbon monoxide. Oxygen should be 
entirely absent, as it should all have been brought into combina- 
tion in its passage through the producer. Its presence in a pro- 
ducer gas may be an indication of leakage in sampling or of 
leakage into the flue prior to sampling. Rarely, if operating 
conditions in the producer are bad, and the fire is thin, there 
may be such a channel formed in the producer that air will 
rush through the producer without its oxygen becoming combined. 
Such a condition will be indicated by extremely high carbon 
dioxide, with low percentages of combustible gases. When a 
producer is running under normal conditions its operation may 
be quite closely checked by the percentage of carbon dioxide 
alone. High carbon dioxide is in practically all cases an un- 
favorable symptom. It may be due to a cold fuel bed in the 
producer caused either by an excess of steam or by slow running, 
it may be due to a thin fuel bed which does not allow sufficient 
time • and contact for the reduction of the carbon dioxide to 
monoxide, and it may be due to channels or chimneys in a deep 
fire which allow uncombined air to get through the fuel bed and 
burn above the coals. 

A cold fuel bed in a producer burning bituminous coal will 
tend to increase the percentage of unsaturated hydrocarbons, 
but in no case will they amount to more than a few tenths of a 
per cent. A hot and thin fuel bed and especially a channeled 
fuel bed will cause the unsaturated hydrocarbons to practically 
disappear, since they are decomposed at the high temperature 
and of all the gases show the greatest avidity for oxygen. 

The carbon dioxide is almost a direct measure of the thermal 
efficiency of the producer, the only exception being its appear- 
ance as the result of the interaction of carbon and steam at a 
relatively low temperature as in the Mond producer where it 
is accompanied by a high percentage of hydrogen. Under other 
circumstances high carbon dioxide means low thermal efficiency 



PRODUCER GAS 153 

for the 70 per cent, of the energy of the carbon which should 
have been converted into the potential energy of the carbon 
monoxide is all changed to the sensible heat of the carbon 
dioxide and accompanying gases. 

5. Heating Value of Producer Gas. — The heating value of 
producer gas may be determined in a calorimeter as described 
in Chapter VII for illuminating gas. A special tip must be 
used on the burner and care be taken to see that the flame 
burns clear. The heating value of producer gas may be as 
low as 100 British thermal units per cubic foot and it frequently 
happens that it does not burn readily in a Bunsen burner. 
The gas must be carefully cooled and cleaned before testing. 
This operation separates tar whose amount and heat value must 
be determined as directed in § 2 of this chapter. The heating 
value of the purified gas may also be calculated from the 
analysis as indicated in § 17 of Chapter VII. The low per- 
centage of unsaturated hydrocarbons in producer gas makes 
the errors of calculation less than is the case with illuminating 
gas. On account of the difficulty in cleaning the gas and in 
keeping a steady flame in the calorimeter, the heating value is 
usually obtained by calculation. 

It is worth while to emphasize again that the heating value 
of the cleaned gas from bituminous coal is lower than that of 
the hot gas which still contains tar vapors and that allowance 
must be made for the tar vapors in calculating the heat value of 
the gas which is used while hot. 

6. Volume of Producer Gas. — It would be very desirable to 
be able to calculate the volume of producer gas per pound of 
coal, as is done in Chapter X for chimney gases. There are, how- 
ever, so many possible reactions in the gas producer and the 
changes in volume are so complicated, especially in a bituminous 
producer, that it is only possible to make such calculations for 
simple cases. 

Assume a producer burning pure carbon in dry air. It is 
manifest that the only products of combustion will be C02,CO 
and N 2 Assume the following composition of the gas 

C0 2 5.5 per cent. 

CO 25 . 6 per cent. 

N 2 68.9 per cent. 



154 GAS AND FUEL ANALYSIS 

The air entering the producer was composed of 79 volumes 
of nitrogen for every 21 volumes of oxygen. The change in 
percentage of the nitrogen in the producer gas is due to changes 
resulting from the union of oxygen with carbon. The first step 
is to trace the changes taking place when 100 volumes of air pass 
through the producer and find the relative volumes of CO2 and 
CO for 79 volumes of N 2 . 



79^ 

■68.9 
79 



C0 2 5.5Xw ^= 6.3 = 6.3vols. 2 



CO 25.6Xggg=29.4 = 14.7 vols. 2 



79_ 
68.9 

100.0 vols. air. 



N 2 68. 9X~ Q ^=79. = 79.0 vols. N 2 



One pound of carbon burning to carbon dioxide requires 32.1 
cu. ft. of oxygen (at 60° F. and 30 in. of mercury pressure) and 
yields 32. 1 cu. ft. of carbon dioxide. One pound of carbon burning 
to carbon monoxide requires 16.05 cu. ft. of oxygen and yields 
32.1 cu. ft. of carbon monoxide. It follows that the weights of 
carbon burning to CO and CO2 are proportional to the volumes 
of the two gases. In the present instance 

C0 2 6.3 = 0^7X100 = 17.7 per cent. 

29 4 
CO 29.4 = ==-= X 100 = 82 . 3 per cent. 
00. / 

One pound of carbon yields 

0.177X32.1= 5.7 cu. ft. C0 2 
0.823X32.1= 26.4 cu. ft. CO 
3.76 X32.1 = 120.7 cu. ft. N 2 

152.8 cu. ft. producer gas. 

The sensible heat will be calculated as in Chapter X. 

5.7X.0268X1000= 153 B. t. u. 
26.4 
120.7 



147. IX- 0180X1000 = 2647 B. t. u. 
2800 B. t. u. 



PRODUCER GAS 155 

Energy in 26.4 cu. ft. of CO 8534 B. t. u. 

Sensible heat in gases 2800 B. t. u. 

Total energy in gas at 1000° F. 11334 B. t. u. 
Efficiency of producer when gas is used at 

1000° F. = ^fj^X 100 = 77.6 per cent. 

7. Efficiency of a Gas Producer. — In the simple instance cited 
above it is easy to calculate the energy contained in the gas. 
The only potential energy in the gas from one pound of carbon 
is contained in the 0.823 lb., which is now in the form of 26.4 cu. 
ft. carbon monoxide. The heating value of this is: 

26.4X323.5-8534 B.t.u. 

The total energy of the coal if burned to carbon dioxide would 
be 14600 British thermal units. If the gas is cooled before being 
burned so that its only energy is the potential energy of the carbon 
monoxide the efficiency of the producer is 

8534 
Yj^qX 100 = 58.4 per cent. 

If the gas is burned while still hot, say at 1000° F., there should 
be credited to the producer also the sensible heat of the gas, as 
calculated in the preceding section where the efficiency was shown 
to be 77.6 per cent. 

The above simple relations do not hold when steam is being 
inj ected into the producer with the air nor when bituminous coal 
is being used as a fuel. On account of the varied possibilities of 
chemical reaction in these cases the volume of the gases cannot 
be calculated from their chemical composition. If the volume 
of the gases is measured by a Venturi meter, or otherwise, then it 
is possible to calculate the sensible and potential energy of the 
gases as indicated in this chapter and the one preceding. 



CHAPTER XII 
ILLUMINATING GAS AND NATURAL GAS 

1. Introduction. — Chemical analysis plays a minor role in 
testing illuminating gas and natural gas. The determination 
of heating value is described in Chapter VII and of candle-power 
in Chapter VIII. The ordinary chemical analysis as described 
in Chapters III and IV usually includes the determination of 
carbon dioxide, unsaturated hydrocarbons, oxygen, carbon monox- 
ide, hydrogen and methane, nitrogen being taken by difference. A 
separate determination of benzene is sometimes desired in illu- 
minating gas and of gasoline vapors in natural gas. Sulphur 
may be called for in both gases. Naphthalene and ammonia are 
frequently determined in coal gas. 

2. Sampling. — The sampling of natural gas and of purified 
illuminating gas usually offers little difficulty, since the gases 
are thoroughly mixed and contain such small amounts of sus- 
pended particles that they are usually negligible. The chief 
point to be observed in sampling from service pipes in cities is to 
see that the gas is allowed to run long enough to flush out the 
pipe and bring to the sampling cock gas which is representative 
of that flowing in the mains. Illuminating gas of high candle- 
power must not become chilled in the sampling process, for there 
is danger of condensing the benzene or other hydrocarbon vapors 
which it contains. Rubber connections are also to be mini- 
mized in sampling because of the solubility of the hydrocarbons in 
rubber. The water used in the sampling vessels must be carefully 
saturated before use, because unsaturated hydrocarbons are 
relatively soluble in water. 

In case unpurified illuminating gas is to be sampled, additional 
precautions must be taken an account of the presence of material 
amounts of ammonia, hydrogen sulphide, carbon dioxide and 
other very soluble gases, as well as suspended tar particles. In 
case it is sufficient to determine what the approximate composi- 
tion of the gas would be after purification it is sufficiently accu- 

156 



ILLUMINATING GAS AND NATURAL GAS 157 

rate to sample in the usual way and trust the water of the samp- 
ling tank to remove the ammonia, hydrogen sulphide and part 
of the carbon dioxide. In case the actual composition of the 
unpurified gas is desired, these soluble constituents must be 
separately determined as indicated in succeeding sections. 

3. General Scheme of Analysis. — Carbon dioxide, unsaturated 
hydrocarbons, oxygen, carbon monoxide, hydrogen and methane 
are usually determined according to the methods of Chapters III 
and IV. In the case of unpurified illuminating gas there may 
be appreciable amounts of hydrogen sulphide absorbed with the 
carbon dioxide. If it is desired to separate the two the hydrogen 
sulphide may be estimated according to the method of § 6. The es- 
timation of carbon dioxide, oxygen and carbon monoxide does not 
present any peculiarities, although emphasis should be laid on the 
necessity of complete removal of the unsaturated hydrocarbons 
before the estimation of oxygen by phosphorus. In the case of 
Pintsch gas it sometimes requires five minutes' shaking with 
bromine water to affect such a complete removal of the hydro- 
carbons that the phosphorus will smoke when the gas is sub- 
sequently passed over it. The determination of hydrogen and 
methane in illuminating gas offers no marked peculiarity. In 
natural gas, vapors of the gasolines may be present and compli- 
cate the calculation. Ethane may also be present in natural gas 
and also in water gas and Pintsch gas. The methods for its 
determination have been discussed in Chapter IV. Nitrogen is 
taken by difference and as the analysis is a rather long and com- 
plicated one, the errors piling up on the nitrogen are apt to be 
material. A direct combustion of the gas with copper oxide, as 
described in § 12 of Chapter IV, gives a more accurate determina- 
tion of the residual nitrogen. 

4. Chemical Composition of Illuminating Gas. — The so-called 
" coal gas" is made by the destructive distillation of coal in closed 
retorts. The composition of the gas is dependent on the compo- 
sition of the coal, the temperature of the retort and to some extent 
its shape and size. There is nothing, however, which distinctly 
characterizes gas from the large retort of the by-product coke 
oven from that of the small horizontal retort of the gas works. 
The oxygen of the coal appears in the gas partly as carbon 
dioxide, partly as carbon monoxide, and partly as water vapor. 



158 



GAS AND FUEL ANALYSIS 



None of it will be evolved as gaseous oxygen. The carbon monox- 
ide will be greater at a high temperature than at a low one, but 
will usually stay between the limits of 5 and 9 per cent. A high 
retort temperature will cause cracking of the hydrocarbons with 
decrease of their percentage and increase of hydrogen. A frac- 
tion of 1 per cent, of free oxygen is normally present in illumin- 
ating gas, partly because of air entering during the operation of 
charging and drawing the retort, partly because of leaks in the 
long condensing system and partly because of liberation of the 
oxygen dissolved in the water used in the scrubbers. In so far 
as this oxygen comes from the air it must be accompanied by four 
volumes of nitrogen. Nitrogen must always be present in this 
amount. Less than four volumes of nitrogen for one of oxygen 
indicates a faulty analysis. The unavoidable nitrogen in the gas 
arising from the destructive distillation of the nitrogenous com- 
pounds of the coal will be between 1 and 11/2 per cent. High 
percentages of nitrogen unaccompanied by a corresponding 
amount of oxygen indicate that suction has been maintained 
on the porous retorts, so that air has been sucked in. The 
oxygen thus brought in contact with the hot gas will at once burn 
with formation of carbon dioxide or water while the nitrogen will 
remain and appear as such in the purified gas. In the manufac- 
ture of water gas a high percentage of nitrogen will result if the 
gasmaker turns the gas into the holder before all the gas pro- 
duced while blowing air is flushed from the machine by the water 
gas. 



TYPICAL ANALYSES OF ILLUMINATING GAS 




Not separately repoiteJ. 



ILLUMINATING GAS AND NATURAL GAS 159 

1. Coal gas of 17 c.p. and 650 B.t.u. 

2. Coke oven gas enriched by benzol to 16.4 c.p. and 626 B.t.u. 
(Proc. Am. Gas Inst, 6, 519 (1911).) 

3. Coke Oven Gas. Fuel Gas (Proc. Am. Gas Inst., 6, 519 
(1911).) 

4. Mixed Coal and Water Gas 15 c.p. and 615 B.t.u. 

5. Carbureted Water Gas of 24 c.p. and 649 B.t.u. (Proc. Am. 
Gas Inst., 7,739 (1912).) 

5. Benzene. — Benzene is a normal constituent of coal gas and 
also probably of water gas, but its amount in unenriched gases is 
always less than 1 per cent., and it is not usually determined. 
Its solubility in water and in caustic soda is slight so that in the 
ordinary analysis the benzene is not absorbed by the caustic but 
passes on to the bromine pipette where it dissolves in the ethylene 
bromide formed in the reaction between ethylene and bromine 
and is therefore estimated with the ethylene as "illuminants." 
As benzene has a very high illuminating power this grouping is 
logical and sufficiently satisfactory for most purposes. 

Hempel recommends that 1 c.c. of absolute alcohol be placed 
in a pipette otherwise filled with mercury. An explosion pipette 
answers well for this purpose. A sample of gas is to be passed 
into the pipette and shaken with the alcohol to saturate it with 
ethylene, and the sample to be analyzed is later passed into this 
same pipette and shaken three minutes. The gas is then drawn 
back into the burette and passed into a second mercury pipette 
containing 1 c.c. of distilled water which removes the alcohol 
vapors. The decrease in volume from the initial reading is 
recorded as benzene. The method is to be considered only an 
approximate one. 

Morton 1 recommends that, after removal of carbon dioxide 
by caustic soda as usual, the gas be passed into an ordinary 
simple absorption pipette containing concentrated sulphuric 
acid (sp. gr. 1.84) and shaken vigorously for one minute. The 
decrease in volume after drawing back into the burette represents 
benzene. Dennis and McCarthy 2 dispute the accuracy of this 
method and propose ammoniacal nickel cyanide as a reagent. 
Their directions for preparation of the reagent are as follows: 

l Jour. Am. Chem. Soc, 28, 1728 (1906). 
2 Jour. Am. Chem. Soc, 30, 233 (1908). 



160 GAS AND FUEL ANALYSIS 

"To 50 grm. of nickel sulphate (NiS0 4 .7H 2 0), dissolved in 75 c.c. of 
water, are added 25 grm. of potassium cyanide dissolved in 40 c.c. of 
water. After the addition of 125 c.c. of ammonium hydroxide (sp. gr. 
0.91) the mixture is shaken until the nickel cyanide has completely 
dissolved and is then allowed to stand at a temperature of 0° for twenty 
minutes. The clear liquid is decanted from the crystals of potassium 
sulphate that have been precipitated, and is treated with a solution 
prepared by dissolving 18 grm. of crystallized citric acid in 10 c.c. of 
water. After the mixture has stood again at 0° for ten minutes, the 
greenish-blue supernatant solution is decanted and is introduced into 
a gas pipette. Two drops of liquid benzene are now added to the re- 
agent through the large tube of the pipette and the pipette is shaken 
until the benzene has combined with the reagent. This is effected in 
two or three minutes. This addition of benzene to the reagent is made 
because it was found that at times a freshly prepared solution of the 
ammoniaeal nickel cyanide did not quantitatively remove benzene 
vapor until it had been used for four or five determinations and had 
absorbed some of the substance." 

The gas after carbon dioxide has been removed by caustic 
is passed into the pipette containing the ammoniaeal nickel 
cyanide solution and drawn back and forth between the burette 
and pipette for about two minutes. It is then passed into a 
five per cent, solution of sulphuric acid and shaken until the 
ammonia is absorbed, which requires about two minutes. Ac- 
cording to the authors, the absorption is quantitative and the 
result unaffected by ethylene. 

The process of Haber and GEchelhauser 1 is based on Bunte's 
observation of the solubility of benzene in ethylene bromide. 
The authors treat the gas with a fresh solution of bromine water 
to which is added, immediately after the reaction, an excess 
of strong potassium iodide. The liberated iodine is titrated 
with thiosuphate and the difference between the figures of 
this titration and those obtained by a blank test on an equal 
volume of the original solution represents the bromine which 
has combined with the ethylene. One cubic centimeter deci- 
normal thiosulphate corresponds to 1.12 c.c. ethylene at 0° C. 
and 760 mm. or to 1.22 c.c. at 60° F. and 29.5 in. mercury 
pressure. The diminution in volume of the gas after the usual 
treatment with bromine water followed by caustic gives the 

1 Jour, fur Gasbel, 43, 347 (1900). 



ILLUMINATING GAS AND NATURAL GAS 161 

sum of the benzene and ethylene. The difference between this 
volume and that indicated by the titration for ethylene gives 
the benzene. 

If a more exact method of estimation of benzene is desired 
and a large sample of gas can be obtained the method of Harbeck 
and Lunge 1 may be used. It consists in aspirating 10 liters 
of the gas through a mixture of equal weights of fuming nitric 
acid and concentrated sulphuric acid. Part of the resulting 
dinitrobenzene crystallizes out after the acids are diluted, 
cooled and neutralized, and may be filtered and weighed. 
The dinitrobenzene remaining in solution is extracted from an 
aliquot portion of the filtrate with ether and also weighed. 

6. Hydrogen Sulphide. — Hydrogen sulphide should be present 
only in minute traces in purified illuminating gas. The usual 
test is an approximate one based on the reaction of hydrogen 
sulphide and lead acetate to form black lead sulphide. A 
strip of white filter paper moistened with colorless lead acetate 
is exposed to the gas and the depth of the resulting black 
stain noted. The details of the test differ widely. The 
New York State Commission prescribes that gas shall show no 
hydrogen sulphide when tested by exposing the paper moistened 
with lead acetate to a current of gas burning at the rate of 
5 cu. ft. per hour. The paper must not become discolored 
after thirty seconds of such exposure. Ramsburg 2 has given 
a full discussion of the various methods of testing for hydrogen 
sulphide in purified gas. 

Hydrogen sulphide is always present in unpurified illuminating 
gas. In the ordinary gas analysis it is absorbed by the caustic 
soda simultaneously with the carbon dioxide and reported 
with it. Its quantitative estimation may be carried out as follows. 
One or more liters of the gas is bubbled through a solution 
of ammoniacal cadmium chloride and the resultant cadmium 
sulphide is filtered. If the precipitate contains much tar it may 
be washed on the filter with benzol. Place filter and precipitate 
in cold dilute hydrochloric acid till dissolved and titrate with 
standard iodine. If the iodine solution is made by dissolving 
1.0526 grm. iodine to the liter, 1 c.c. will be equivalent to 1/10 

1 Zeit. fur anorg. Chem., 16, 41 (1898). 
Proceedings Am. Gas. Inst., 4, 453, 1909. 



162 GAS AND FUEL ANALYSIS 

c.c. of hydrogen sulphide measured damp at 60° F. and under 
30 in. of mercury pressure. A solution of ten times the above 
strength is more convenient if much hydrogen sulphide is present. 

A rapid approximate estimation of hydrogen sulphide may be 
made in the Bunte gas burette described in § 4 of Chapter V. 
The burette is first filled with water containing a little thin 
starch paste to act as indicator, and the sample of gas drawn in 
and measured rapidly to prevent error due to the solubility of 
the hydrogen sulphide in the water of the burette. Standard 
iodine solution is now admitted from the reservoir at the top of 
the burette, about a cubic centimeter at a time, until the blue 
color formed by the reaction between the iodine and starch 
persists after repeated shaking, showing that the hydrogen sul- 
phide has all been oxidized. If iodine solution of the concentra- 
tion given above has been used, the volume of hydrogen sulphide 
may be read directly from the volume of iodine used, which must 
be obtained by measuring the iodine solution still remaining in 
the reservoir of the burette. Tutwiler has modified the burette 
by making the reservoir longer and graduating it so that the 
iodine used may be read directly. 

7. Total Sulphur Compounds. — Illuminating gas and almost 
all other gases used for fuel contain, in addition to hydrogen sul- 
phide, compounds of sulphur and carbon such as carbon bisul- 
phide and more complex compounds like the mercaptans. These 
compounds are usually estimated after complete combustion in 
which process all the sulphur, whatever its previous combination, 
is converted into sulphur dioxide and sulphur trioxide. These 
gases are absorbed, oxidized to sulphuric acid and weighed as 
barium sulphate. Care must be taken to see that the air used for 
combustion, which is usually ten times the volume of the gas, 
is itself free from sulphur compounds, and that combustion is 
complete. The form of burner and absorption apparatus is 
immaterial, except for convenience. The most usual form is that 
of Drehschmidt which is illustrated in Fig. 36. Harding 1 and 
Jenkins 2 have both described modifications of the apparatus 
which may be made from ordinary laboratory apparatus by any- 
one with some skill in blowing glass. 

1 Jour. Am. Chem. Soc, 28, 537 (1906). 

2 Jour. Am. Chem. Soc, 28, 542 (1906). 



ILLUMINATING GAS AND NATURAL GAS 



163 



In the Drehschmidt apparatus the gas is measured in an 
experimental meter and burned in a Bunsen burner which is 
enclosed in a metal case and is supplied with air which has been 
purified by passing through a tower A in contact with dilute 
caustic soda. The metal case surrounding the burner terminates 
at the level of the burner top and is continued as a glass chimney 
drawn down at the top and terminating in a tube leading to a 
train of absorption bottles. The construction of the apparatus 
is readily evident from the cut. 

In making a test about 25 c. c. of dilute Na 2 C0 3 (approximately 




Fig. 36. — Drehschmidt's sulphur apparatus. 



5 per cent.) is poured into each of the absorption cylinders and 
to the first two are added a drop or two of bromine to oxidize 
the SO2 vapors. The train is then connected to an aspirator. 
The burner itself is removed from the case, lighted and adjusted 
to a consumption of about 1 cu. ft. of gas per hour. The aspira- 
tor is then started and adjusted so that the air bubbles rapidly 
through the absorption train and the lighted burner is slipped 
into its case where it fits snugly. If all the adjustments are 
properly made the gas continues to burn with a clear blue flame 
and the products of combustion are sucked into the absorption 
train where the S0 2 formed in combustion is absorbed and oxi- 



164 GAS AND FUEL ANALYSIS 

dized to Na2SC>4. The proper adjustment of the flow of air to 
keep the burner alight offers difficulties to the beginner which 
only practice can overcome. After 1 cu. ft. of gas has been 
burned, the burner is removed from the casing and any moisture 
which has condensed in the glass chimney is rinsed into the car- 
bonate from the absorption vessels. The carbonate is acidified 
with HC1, boiled and treated with BaCl 2 in the usual manner to 
precipitate the sulphate. 1 grm. BaS0 4 = 0.1373 grm. S. or 2.119 
grains S. The result is usually reported as grains sulphur per 
100 cu. ft. of gas measured under standard conditions. 

8. Naphthalene. — The amount of the hydrocarbon, naphthalene 
Cio Hs, usually present in gas is less than one-tenth of 1 per cent. 
Its small amount would make it unworthy of consideration 
were it not for its disagreeable property of causing stoppages in 
gas mains. Its estimation is therefore sometimes demanded as 
one of the steps in controlling the manufacturing process. 

The usual method for purified gas is that devised by Coleman 
and Smith 1 , who based their method on Klister's 2 method for 
separating naphthalene from other hydrocarbons. The method 
depends upon the property which naphthalene possesses of combin- 
ing molecule for molecule with picric acid to form an insoluble 
compound. In the author's laboratory it has been customary 
to make the picric acid about 1/20 normal, which is an almost 
saturated solution, and to use as alkali Ba(OH) 2 1/5 normal, 
with phenolphthalein or lacmoid as indicator. The color change 
is not difficult to observe, but the same conditions must always 
be observed in the analysis that are maintained in the standardiza- 
tion. When the gas to be tested has been purified and there is 
no danger of naphthalene deposition at room temperature the gas 
may be passed through a wet experimental meter, then through 
a wash bottle containing dilute tartaric or other non-volatile 
acid to remove all traces of ammonia, then through a bottle con- 
taining water to stop acid which might have spattered over and 
then through a bulbed gas washing tube with about ten bulbs 
containing 50 c.c. of the standard picric acid. A yellow precipi- 
tate betrays the presence of naphthalene. After five or more 
cubic feet of gas have been bubbled through the apparatus, the 

1 Jour, of Gas Lighting, 75, 798 (1900); 80, 1277 (1902). 

2 Berichte, 27, 1101, 



ILLUMINATING GAS AND NATURAL GAS 165 

bulbed tube is disconnected and washed into an Erlenmeyer flask 
of about 150 c.c. capacity, the bulbed tube being rinsed with 
50 c.c. of picric acid from a pipette. The flask is then closed 
with a rubber stopper carrying a glass tube through which most 
of the air is sucked from the flask by a filter pump in order that 
it may not blow up when heated later. The evacuated flask is 
then placed in a water bath which is maintained at the boiling 
temperature for an hour. Rutten 1 says that it is sufficient to 
heat to 40° C. for half an hour. The flask is then removed and 
allowed to cool when the naphthalene picrate will have recrystal- 
lized as a definite compound CioH 8 . C6H 2 OH(N02)3. This is 
filtered off and an aliquot part of the filtrate is titrated with 
alkali. The difference between the amount of alkali required 
for this titration and that which would have been required on a 
blank titration gives, when calculated for the whole volume of 
picric acid present, the naphthalene absorbed. One cubic centi- 
meter of N/5 Ba(OH) 2 is equivalent to 0.0256 grm. naphthalene. 
If great accuracy is not required the heating of the naphthalene 
picrate in its solution may be dispensed with. 

When gas freed from tar particles but otherwise unpurified 
is to be tested for naphthalene, it must be freed from ammonia 
and hydrogen sulphide, which affect the titration. The gas 
must not be allowed to cool below the temperature of the main 
during this purification process or naphthalene may deposit. 
The purifying train may be placed in an oven such as that shown 
in Fig. 38, placed so that it is in close proximity to the main 
and heated to the desired temperature. The first washer 
may contain lead acetate, the second a dilute acid and the third 
water. The tube with picric acid must not be placed in the 
oven since naphthalene will not be absorbed by a warm solution, 
but must be immediately outside. If naphthalene is deposited 
in the glass connecting tube it may be vaporized and driven 
forward by heat. Where much naphthalene is present two 
bulbed tubes should be used in series and if much precipitate 
appears in the second tube the liquid in the first tube should 
be renewed since a dilute solution of picric acid does not remove 
naphthalene completely. The precipitated naphthalene is es- 
timated in the same manner as in the case of purified gas. 

1 Jour, fur Gasbel, 52, 694 (1909). 



166 GAS AND FUEL ANALYSIS 

Where naphthalene must be estimated in crude gas still 
containing suspended tar and it is desired to separate the 
naphthalene present as vapor in the gas from that which is 
carried in the dissolved tar particles, the method becomes 
still more complicated. The method devised by the author 1 
to separately determine the naphthalene present as vapor in 
the gas from that which is carried in the dissolved tar particles 
involves precipitation of naphthalene as the picrate with 
subsequent recovery of the naphthalene. Considerable care 
is necessary in sampling gases which contain tar, if it is desired 
to distinguish between the naphthalene actually present as 
vapor in the gas and that existing dissolved in the fine, mist- 
like particles of tar suspended in the gas and which will be 
removed later by mechanical scrubbing. It is out of the question 
to collect a tank of gas, say from the foul main, and transport 
it to the laboratory for examination. The condensation and 
separation of tarry products in the gas holder would nullify 
the value of the figures obtained. It is necessary to separate 
the suspended tar and remove the naphthalene before change of 
temperature has had time to alter the conditions prevailing 
at the point of sampling. This requires that the tar vapors 
shall be mechanically filtered from the gas without any change 
in temperature. The result is attained by inserting horizontally 
into the main a glass tube about 1/2 in. in diameter filled with 
glass wool or asbestos fiber. This tube should project into the 
main at least 6 in. and at as short a distance outside the main 
as possible should connect with the picric acid absorbing train, 
and then with a gas holder of about 1 cu. ft. capacity and of 
known volume as shown in Fig. 2 of Chapter I. The strong 
solvent power of tar for naphthalene renders it absolutely 
essential that the gas shall not be scrubbed by passing through 
cold tar, as would be the case if the tube for separation of the 
tar were placed outside the main and, for example, connected 
to a pet cock. After the sample has been drawn, the picric 
acid contains the naphthalene and tar which were still present 
in the gas as vapor. The solution and precipitate is washed 
into a 200 c.c. Erlenmeyer flask and treated with alkali to neu- 
tralize the picric acid. It is our custom to add here an excess 

^Proc. Mich. Gas. Ass., 1904; 1905, 83. 



ILLUMINATING GAS AND NATURAL GAS 



167 



of solid alkali, making an almost saturated solution when hot, 
merely to prevent so much moisture being carried into the dry- 
ing tube. As this addition of solid alkali makes the solution hot, 
it should not be added until just before the apparatus is con- 
nected up so as to avoid loss of naphthalene. If the glass con- 
necting tube contains naphthalene deposited from the gas by 
condensation the tube should be broken into fragments and 
dropped into the same flask. 

The flask is then corked with a stopper carrying two glass 
tubes, one long enough to reach nearly to the bottom of the 
flask and the other terminating just below the cork and extending 
above the cork to make connections to the tube containing 



CaO 




O c3 O 3 O 3 




6Iass Sleeve-' 
Covered with 

Rubber 




Fig. 37. — Details of naphthalene train. 



lime and phosphorus pentoxide as shown at A of Fig. 37. At 
the other end of the drying tube B close connection is made to a 
small weighed U tube C which can be immersed in ice water. 
The tube containing the asbestos and tar is connected directly 
to a similar drying tube and U tube. The arrangement of the 
train is shown in Fig. 37 and the whole set in the oven is 
shown in Fig. 38. The oven is heated to 70°-80° C. and air 
slowly drawn through the system, volatilizing the naphthalene 
and moisture in the tar. The moisture is taken up by the 
dryer — -lime and phosphorus pentoxide — while the naphthalene 
passes on to be frozen out in the U tube placed directly out- 
side of the oven in a trough filled full of cracked ice. The analysis 



168 



GAS AND FUEL ANALYSIS 



is complete when the weight of the naphthalene U tube becomes 
constant or very nearly so at consecutive weighings after a 
two- or three-hour interval. The volatilization of the naphthalene 
from the gas is usually complete in six hours. The time required 
for an analysis of tar varies with the amount of tar in the sample 
and usually takes thirty or forty hours for standpipe samples 
when the weight of tar amounts to 8 or 10 grm. When the 
analysis is complete, the tar volatilizing tube is again weighed, 
the loss giving the weight of moisture and naphthalene given 
off. Having the weight of naphthalene in the U tube, we have 
the weight of moisture also, which, however, is at best only 




Fig. 38. — Oven for naphthalene determinations. 



approximate, because there is always more or less light oil, such 
as benzene, given off from the tar with the moisture and naphtha- 
lene, which cannot easily be estimated. Finally the volatilizing 
tube is set in a Soxhlet extractor and the remaining contents 
extracted with chloroform until free of all soluble material. 
After drying, the tube is weighed, this giving the weight of free 
carbon in the tar. 

The oven used is of galvanized iron and is 20 in. high by 16 in. 
wide by 14 in. deep. It is shown in Fig. 38 and is arranged so 
that eight samples may be worked at a time. The drying train 
consists of a heavy glass tube about 1/2 in. internal diameter 
and 12 in. long. It contains broken lime for about two-thirds of 



ILLUMINATING GAS AND NATURAL GAS 169 

its length and phosphorus pentoxide thoroughly incorporated in 
glass wool for the other one-third. This introduction of the glass 
wool with the phosphorous pentoxide prevents the gas from 
forming channels in the latter and thus aids in rendering the ex- 
traction of moisture complete before reaching the napthalene 
U tube. The lime used must be extremely rapid in its reaction 
with water in order to avoid too great expense for phosphorus 
pentoxide. It may be readily made by igniting crushed lime- 
stone to a dull red heat for two hours in a muffle. If the lumps of 
lime are too small, the expansion attendant upon their slacking 
will crack the tube. If the lumps are too large, the gas will not be 
dried sufficiently. A satisfactory mixture is obtained by taking 
everything that will pass a four-mesh sieve and will not pass a 
twelve-mesh. Connection with the naphthalene U tube is made 
as shown in Fig. 37 at C, through a glass sleeve made air tight by a 
piece of rubber tubing placed over the whole. This prevents 
the naphthalene from coming in contact with the rubber. It is 
well known that rubber absorbs naphthalene. Nevertheless, 
it has been found safe to use rubber stoppers in the volatilizing 
oven. Rubber stoppers in frequent use absorb all they can 
take up and after a few runs cause no further trouble. 

This method allows the estimation of naphthalene as vapor in 
the gas, and of water, non-volatile tar, free carbon and naphtha- 
lene in the suspended tar. The separation of the water and non- 
volatile tar is not very accurate, the light oils which are vaporized 
by the air drawn through being reported as water. The estima- 
tion of naphthalene is, however, quite accurate. The air passing 
through will leave the system saturated with naphthalene at the 
temperature of ice water, but this loss need not amount to over a 
milligram for each ten hours' run. It is possible that the naphtha- 
lene may be contaminated by other hydrocarbons and the naphtha- 
lene deposit is sometimes slightly oily and has a low melting 
point. 

9. Ammonia. — Crude coal gas before scrubbing may contain as 
much as three-quarters of a per cent, of NH 3 by volume. After 
the gas has traversed the scrubbers the amount of ammonia 
should be reduced to a trace. The amount of NH 3 permissible 
in purified gas in Massachusetts and New York is 10 grains per 
100 cu. ft. It is not difficult to conform to this requirement. 



170 GAS AND FUEL ANALYSIS 

The gas to be tested is bubbled through standard acid, suc- 
tion being produced by an aspirator holding a cubic foot, which 
also acts as a measuring device. The excess of acid is then 
titrated back with standard alkali, cochineal being used as an 
indicator. If the gas contains much suspended tar the end of 
the titration cannot be observed sharply and it is necessary to 
make the solution alkaline and redistill the ammonia into standard 
acid before titrating. One cubic centimenter of N/io acid equals 
0.017 grm. NH 3 . 

10. Cyanogen. — Cyanogen compounds exist in small amounts 
in unpurifled gas. In the purification process they are partly 
removed in the ammonia scrubbers and largely in the iron-oxide 
purifiers or in special scrubbers containing compounds of iron. 
The gas is estimated by bringing it into contact with an alkaline 
solution carrying suspended ferrous hydroxide and titrating the 
resultant ferrocyanide. The method according to Mueller 1 is as 
follows : 

"To determine the amount of cyanogen in gas, the cyanogen is 
converted into potassium ferrocyanide by passing the gas through a 
caustic potash solution containing freshly precipitated ferrous hydrate 
in suspension. After filtering, the potassium ferrocyanide is determined 
in the clear solution by acidifying and titrating with a standard solution 
of zinc sulphate until all ferrocyanide has been precipitated as zinc 
ferrocyanide. The end reaction is determined as follows: A drop of 
a 1 per cent, solution of ferric chloride is put on a piece of white filter- 
paper absolutely free from iron. A drop of the liquid being tested is 
then put on the paper near the drop of ferric chloride so that the liquor 
as it spreads out on the paper will come in contact with the ferric 
chloride. Care must be taken that the precipitate of zinc ferrocyanide 
does not come in contact with the iron solution. As long as there is 
any ferrocyanide left in solution, a blue color will appear where the 
two drops come in contact due to the formation of prussian blue. 
When all ferrocyanide has been precipitated this color will no longer 
appear, which indicates the end point of the titration. The zinc sul- 
phate solution is made by dissolving approximately 5 grm. of pure zinc 
sulphate in 1 liter of water with the addition of 10 c.c. of sulphuric 
acid. This solution is standardized with a solution of 10 grm. of potas- 
sium ferrocyanide (K 4 Fe(CN) 6 . 3H 2 0) dissolved in water and diluted 
to 1 liter. Twenty-five cubic centimeters of the potassium ferrocyanide 

1 Proc. Am. Gas Inst., 5, 249 (1910). 



ILLUMINATING GAS AND NATURAL GAS 



171 



solution are put into a beaker and titrated with the zinc sulphate 
solution, the end reaction being determined as above. One cubic 
centimeter of the ferrocyanide solution is equivalent to 0.0570 grains 
of cyanogen, from which the value of the zinc solution is calculated. 

"To test for cyanogen in gas put 15 c.c. of a 10 per cent, ferrous 
sulphate (FeS0 4 . 7H 2 0) solution into each of three wash-bottles. Add 
15 c.c. of 20 per cent, caustic potash solution to each bottle and pass 
about 3 cu. ft. of gas through these bottles at the rate of about 1 cu. 
ft. per hour. Rinse the contents of the bottles into a beaker, add 20 
c.c. more of the caustic potash solution and heat to boiling. Filter 
and wash with hot water until a few drops of the filtrate no longer 
show a blue color when acidified and tested with a drop of 1 per cent. 
ferric chloride solution. Transfer the filtrate to a 500 c.c. graduated 
flask, dilute to the mark and shake well. Take 
100 c.c. of this solution and transfer to a beaker 
by means of a pipette. Slowly add dilute sul- 
phuric acid (sp. gr. about 1.5) stirring constantly 
until the solution becomes slightly acid toward 
litmus. Then run in the zinc sulphate solution 
a few drops at a time until the drop test as ex- 
plained above shows that the ferrocyanide has 
all been precipitated. From the amount of zinc 
sulphate solution used the amount of cyanogen 
in the gas is calculated." 

11. Specific Gravity. — The simplest 
method of determining the specific gravity 
of gases makes use of the law that different 
gases streaming through a given orifice at 
the same temperature and pressure flow 
through the orifice at a rate inversely pro- 
portional to the square root of their specific 
gravity. Since the time of flow is inversely 
proportional to the rate, the specific gravity 
becomes proportional to the square of the 
time of flow. Bunsen devised an inge- 
nious instrument to measure specific grav- 
ities in this way and Schilling later gave it -the form which is 
shown in Fig. 39. It consists of a glass cylinder open at the bottom 
and fastened to a metal base which keeps it vertical within the 
larger cylinder of water. It is closed at the top by a metal cap 
carrying two cocks. A is for the introduction of the gas to be 




''///////////////////V//S/7S"'''' 



Fig. 39.— Schilling's 
specific gravity appa- 
ratus. 



172 GAS AND FUEL ANALYSIS 

tested. B is a three-way cock which in one position discharges 
the gas through a side arm to flush the apparatus. When this 
cock is in the vertical position the gas passes through a small 
opening in a platinum plate at C. The apparatus should be 
standardized against air each time it is used. The calibration 
is made by opening the air cock and raising the inner cylinder 
until it is nearly out of water. It will then be filled with air. 
After closing both cocks it is to be again lowered into the cylinder 
of water. The observer opens the cock B so that the air streams 
out through the capillary platinum opening, starts a stop watch 
as the meniscus passes the lower mark on the gas tube and stops 
the watch as it passes the upper mark. The instrument is now 
thoroughly flushed with gas and the time required for the volume 
of gas between the two calibration marks to stream out of the 
opening is determined in the same way. The calculation then 
follows from the formula 

sp. gr. gas_t 2 gas 
sp. gr. air ~~ t 2 air 

12. Natural Gas. — Natural gas is ordinarily distributed and 
used without any attempt at purification. There is, therefore, 
much less call for analysis of this product. The most important 
determination is that of heating value, which is carried out in a 
gas calorimeter as described for illuminating gas in Chapter VII. 
If the burner of the calorimeter is adjusted for coal gas it will 
have to be readjusted for the natural gas and a different tip may 
have to be inserted. The volume of the natural gas should be 
controlled to give about the same rise in temperature in the calor- 
imeter as is desirable for coal gas. When a knowledge of the 
total sulphur is desired it is estimated by the method of § 7 of 
this chapter. The chemical composition of the gas is character- 
ized by very small amounts of C0 2 , 2 and unsaturated hydro- 
carbons. The chief constituent is usually methane with variable 
amounts of ethane and higher homologues. Some gases contain 
enough gasoline vapors to make it pay to condense them by com- 
pression and refrigeration. Burrell 1 reports that the specific grav- 
ity of the gas gives good indication of its value for this purpose. 
Pittsburgh natural gas with a specific gravity of 0.64 when com- 

1 Bull. 88, U. S. Bureau of Mines. 



ILLUMINATING GAS AND NATURAL GAS 



173 



pared with air. does not yield commercial quantities of gasoline. 
Gases with specific gravity of 0.95 to 1.60 yield commercially 
from one to five gallons of 75 to 98° Be gasoline per thousand 
cubic feet of gas. Heavy oils of various sorts may also be used 
as absorbents for gasoline vapors. Since, however, methane is 
also decidedly soluble in oils the absorptive value of the oil for 
methane must be previously determined. The United States 
Geological Survey 1 gives the following as the average composi- 
tion of natural gas from the three large fields of the United States. 



Average, 
Pa. and W. Va 



Average, 
Ohio and Ind. 



Average, 
Kas. 



C0 2 

H 2 S 

2 

CO 

H 2 

CH 4 

Other hydrocarbons. 
N 2 



0.05 
0.00 
trace 
0.40 
0.10 
80.85 
14.00 
4.60 



0.20 
0.15 
0.15 
0.50 
1.50 
93.60 
0.30 
3.60 



0.30 
0.00 
0.00 
1.00 
0.00 
93.65 
0.25 
4.80 



Mineral Resources of U. S., 1909, 2, 297. 



CHAPTER XIII 
LIQUID FUELS 

1. Introduction. — The liquid fuel most frequently used is 
petroleum in either a crude or semi-refined form. Coal tar and 
tar products rank next in importance. Alcohol may become 
important in the future. These fuels, which are to be burned 
directly, are usually blown into the furnace in a fine spray by 
means of steam or compressed air. The main points to be deter- 
mined are their heating value, their behavior in the burner and 
the relative danger which attends their storage. Fuels which 
are to be vaporized before combustion, as is the case in internal 
combustion engines, kerosene lamps, etc., require more elaborate 
tests which do not come within the scope of this book. 

2. Sampling. — The main difficulty in getting a representa- 
tive sample of liquid fuel is caused by the layer of water and sedi- 
ment which frequently accumulates on the bottom of a tank of 
oil or on the surface of one of tar. The main portion of the liquid 
may also be stratified if various grades have been mixed. The 
U. S. Bureau of Mines 1 recommends that the oil be sampled as 
delivered and that either a small stream be run off continuously 
to a drum from which, after mixing, a smaller sample shall be 
taken, or that at regular intervals a small dipperful shall be taken 
from the main stream and placed in a mixing drum. Where it is 
necessary to sample from a small tank, a proportional sample may 
be obtained by slowly lowering a glass tube vertically through the 
oil till the lower end rests on the bottom. If now the upper 
end be closed by the thumb a column of liquid may be drawn 
out which represents the composition of the vertical section at 
the point of sampling. For large tanks the glass tube is replaced 
by one of tin carrying throughout its length a stiff wire on whose 
lower end is a tapering cork. When the cork hits the bottom 

1 Technical Paper 3, Bureau of Mines. Specifications for the Purchase of 
Fuel Oil for the Government twih Directions for Sampling Oil and Natural 
Gas. 

174 



LIQUID FUELS 175 

of the tank as the tube is lowered, it is forced up into the tube, 
sealing the latter so that the sample may be drawn to the surface 
without leakage. In default of a sampling tube a corked empty 
bottle with a string tied to the cork may be lashed to a stick 
and be used. When the bottle has been lowered to the desired 
depth a pull on the string removes the cork and allows the bottle 
to fill with oil which can be withdrawn and form part of a com- 
posite sample. 

3. Heating Value. — The heating value of liquid fuels may be 
determined in either the bomb or Parr calorimeter in accordance 
with the general directions in Chapters XVI and XVII. Some 
difficulty in combustion will be experienced since all the com- 
pounds volatilize very rapidly during combustion and there is 
danger that some of the vapors may break through the flame 
zone without being completely burned. Incomplete combustion 
may usually be detected on opening the calorimeter by the odor, 
and the presence of soot on the inside of the cover. The difficulty 
becomes greater with volatile liquids like gasoline or alcohol, both 
because of their greater volatility in the calorimeter and because 
of the difficulty of weighing the sample accurately. 

Slightly volatile liquids such as tar and heavy petroleum oils 
may be weighed directly into the capsule of the bomb calorimeter 
and burned completely, if oxygen under 25 atmospheres pressure 
is used. It is advisable to place on the oil a small weighed pellet 
of sugar or benzoic acid to start combustion. More volatile 
liquids must be weighed in thin- walled bulbs of about 0.5 c.c. 
capacity with capillary necks which the analyst may blow for 
himself out of fine glass tubing. These are filled by warming 
the weighed bulb and immersing the open neck in the liquid. 
Contraction of the air in the bulb draws up a little of the liquid 
and by repetition of the process the bulb may be filled. The capil- 
lary neck may then be sealed close to the bulb with a small blow- 
pipe flame. The increase in weight of the bulb, plus the portion 
of the neck fused off gives the weight of oil in the sample. The 
sealed bulb is placed on the capsule of the calorimeter and around 
it is piled about 0.25 grm. of sugar or benzoic acid in contact with 
the fuse wire. The combustion of this material breaks the bulb 
and ignites the contents. Richards and Jesse 1 have shown that 
1 Jour. Am. Chem. Soc, 32, 268 (1910). 



176 GAS AND FUEL ANALYSIS 

even this method fails to give complete combustion with volatile 
liquids like benzene. They recommend the following procedure 
as successful. 

"The benzene in a very thin glass bulb was placed in the bottom of 
a narrow platinum crucible, 2 cm. in diameter and 2.5 cm. high. A few 
millimeters above the bulb was fixed a small platform of thin glass 
bearing a weighed quantity of powdered sugar. The passage of a cur- 
rent through the coil of iron wire ignited the sugar, which in its turn 
burst the bulb and ignited the benzene at a moment when the whole 
top of the narrow crucible was filled with flame from the burning sugar. 
Thus none of the benzene vapor could escape ignition. The trouble 
with the old method had been that the larger crucible was too wide. 
Moreover, the sugar had been beneath the benzene instead of above 
it, so that some of the benzene escaped unconsumed. The amount 
which thus escaped was greater when there was more nitrogen present 
than when there was less. Obviously, with non-volatile compounds 
like sugar the width of the crucible would make no difference." 

Gelatine capsules such as used by pharmacists have also been 
recommended as containers for volatile oils, but their moisture 
content changes so rapidly in the air that it is difficult to keep 
constant the necessary correction factor for the gelatine. 

The heating value of oils may also be determined in the Parr 
calorimeter, which is described in Chapter XVII. Non-volatile 
oils may be weighed directly into the calorimeter which already 
contains the peroxide mixture, and mixed thoroughly with the 
charge by means of a stiff wire. Volatile liquids may be placed in 
the calorimeter in a thin-walled glass bulb as directed for the 
bomb calorimeter, and the charge of chemicals placed upon it. 
The calorimeter is then closed with the cap provided and shaken 
violently until the bulb is broken and the oil is mixed with the 
peroxide. A correction in addition to those specified in Chapter 
XVII must be deducted for the heat liberated by reaction between 
the peroxide and the glass of the bulb. Professor Parr gives 
this correction as 0.017° C. per 0.1 grm. glass. 

The weight of oil taken should be about 0.3 grm. and the charge 
10 grm. of Na 2 2 and 1 grm. of KC10 3 . The use of 0.2 grm. 
benzoic acid is also advantageous. Care must be taken that crude 
petroleum and tars do not carry much emulsified water, for the 
water reacts with the peroxide with evolution of heat. In ex- 



LIQUID FUELS 



111 



treme cases a violent explosion may take place, wrecking the 
calorimeter. 

If the oil is of such a type that it may be burned without smoke 
in a burner without a wick and there is at least a pint of the oil 
available, the most convenient method of determining heat 
value is in a calorimeter of the Junkers type whose use for deter- 
mining the heating value of gases is described in Chapter VII. 
The apparatus as modified for liquids requires a suitable burner 
for the oil which hangs upon a balance during the determination 




Ftg. 40. — Junkers' calorimeter for heating value of oils. 

as shown in Fig. 40. The lamp as shown in the illustration requires 
150-200 c.c. of oil. To start the lamp the cup L is filled with 
alcohol which is lighted to preheat the burner head, n. When the 
alcohol is nearly burned away, air-pressure is placed upon the 
liquid by a hand pump connected to m. The oil rises in the bur- 
ner, vaporizes and ignites in the alcohol flame. The pumping is 
continued until a freely-burning blue flame results when the pump 
is disconnected. After the water is flowing normally through the 
calorimeter, the lighted lamp is inserted and centered in the com- 
bustion space. When equilibrium has been reached, the balance 

12 



178 GAS AND FUEL ANALYSIS 

is brought to zero by proper adjustment of weights in the pan 
and the experiment started. After a definite weight of oil, 
usually 5 or 10 grm., has been burned, the experiment is inter- 
rupted and from the rise in temperature and the weight of 
water heated the heating value of the fuel may be calculated. 
The details and precautions are in general the same as given for 
the gas in Chapter VII. 

4. Specific Gravity. — The specific gravity of petroleum products 
is less than 1 and is usually reported on the Baume scale 
for liquids lighter than water. Tar is usually heavier than 
water and its specific gravity is reported directly. If a sufficient 
quantity of material is available and it is not too viscous, the 
specific gravity may be determined with approximate accuracy 
by a hydrometer spindle. If greater accuracy is required or 
if only a small sample is available a pycnometer or Westphal 
balance must be used. If a specific gravity on water-free material 
is demanded, the oil must be put into a flask without the addition 
of any diluent and distilled slowly till the water is off. The 
oil distilled is then separated from the water and returned to 
the residue in the still after it has cooled. A comparison of the 
Baume scale for liquids lighter than water and the corresponding 
specific gravities is given in Table VIII of the Appendix. 

5. Moisture. — The various methods for the determination 
of water in petroleum have been carefully examined by Allen 
and Jacobs. 1 They recommend a method which involves the 
measurement of the hydrogen evolved by the action of the 
water on metallic sodium and also the method of distillation, 
either with or without the addition of water-saturated toluene 
or xylene. The latter method will probably give the better 
results in inexperienced hands. It may be used for tar as 
well as petroleum products. The toluene is added to diminish 
the viscosity of the mass and lessen the danger of foaming 
and bumping. Instead of toluene, xylene or petroleum benzine 
with a boiling-point of 110 to 150° C. may be used. The diluent 
must, however, be first shaken with water and then allowed 
to stand until perfectly clear in order that it may not dissolve 
any of the water of the sample. The sample of about 100 
grm. is weighed into a distilling flask holding at least 500 c.c. 

1 Technical Paper 25, U. S. Bureau of Mines, 1912. 



LIQUID FUELS 179 

and to it is added a roughly measured volume of 100 c.c. of 
the diluent or 200 c.c. if the sample is very viscous. The 
distillation is started slowly and continued until the distillate 
no longer comes over turbid and approximately as much oil 
has distilled as was added as a diluent. The distillate is caught 
in a graduated cylinder and the volume of water read directly 
after sufficient time has been given for it to settle by gravity. 
Allen and Jacobs state that the method may be made accurate to 
approximately 0.033 grm. water for each 100 c.c. of benzene and 
oil in the distillate. 

The details of a similar method for the determination of 
water in tar as used in the laboratories of the Barret Manufac- 
turing Company have been published by S. R. Church. 1 He 
specifies exactly the dimensions of the still, the manner of 
placing the thermometer and other details. The distillation 
is to be continued until the thermometer in the vapor has 
reached 205° C. He recommends a convenient form of graduated 
separatory funnel for the distillate and states that a clean 
separation of the oil and water can be obtained if 25 c.c. of 
benzene is introduced into the separatory funnel before the 
distillation is started. 

6. Proximate Analysis. — A proximate analysis in the sense 
in which it is used in coal analysis is not often made on liquid 
fuels because they are so largely volatile that the test has 
little meaning. The ash gives some measure of suspended 
earthy solids and in the case of tar, the fixed carbon gives an 
indication of the amount of "free carbon" in the tar. It is 
necessary to modify the standard method for volatile matter 
in coal by heating the crucible gently until all foaming has 
stopped. 

7. Suspended Solids. — Suspended solids which in the case 
of crude petroleums usually are earthy matters and in the 
case of tars are fine particles of coke forming the so-called 
"free carbon" are separated by filtration and washing. The 
oil or tar is first filtered through a 30- or 40-mesh sieve to remove 
coarse foreign bodies accidentally included. A weighed sample 
of 5 or 10 grm. is then diluted with pure benzene or toluene 
until it will filter readily. The solution is filtered through a 

1 Jour. Ind. and Eng. Chem., 3, 228 (1911). 



180 GAS AND FUEL ANALYSIS 

pair of weighed heavy filter papers or through a Gooch funnel 
and the filter washed with more of the warm solvent until the 
extraction is complete. The filter is then dried at 105° C. 
The increase in weight gives suspended solids. If there is 
much water in the liquid being examined it may be retained 
on the filter in the form of drops during the first filtration. 
This water may be driven off by gentle heating and the extrac- 
tion of soluble material then continued. 

8. Flash Point. — The flash point of an oil indicates the tem- 
perature at which the oil gives off combustible vapors with 
sufficient rapidity to form an explosive mixture with the air 
above it. The flash point will depend upon the rate of heating 
the oil, the volume of air above it, the rapidity with which the 
air is replaced and many other variables. It is evident that 
the conditions must be closely specified in order that results 
may be of value. Unfortunately there is no standard method 
as there is for the determination of volatile matter in coal. 
The figure is of great importance with kerosene oil and most of 
the states have definite and for the most part different regulations 
on the subject. The older forms of apparatus were open cups. 
The more modern forms have closed cups and are best exam- 
plified by the Abel cup and its modifications. This consists 
of a brass cup 2 in. in diameter set in an air bath which in turn 
sits in a relatively large water bath to insure even heating of 
the oil. The oil cup is covered by a brass cover carrying a 
thermometer and a sliding door. At a touch of a spring the 
door opens and a small lamp carrying a minute flame is lowered 
into the air space above the oil. This operation is repeated 
as the temperature rises until a slight puff which blows the 
flame out indicates that there has been an explosion. This 
subject belongs in the domain of the " burning" oils rather 
than the "fuel" oils and the reader is referred to books on oil 
analysis for details. 



CHAPTER XIV 
SAMPLING COAL 

1. General Consideration. — However accurate an analysis 
of coal may be, the results are of little value and are often worse 
than useless if the sample submitted to the analyst is not a repre- 
sentative one. Elaborate methods have been worked out for 
sampling gold and silver ores but cost precludes the application 
of anything but the simplest methods to coal. It is manifest 
that it is unwise to spend ten cents a ton to determine whether 
the price is two cents a ton too high. If we assume a shipment of 
a single car of coal weighing forty tons, which must be sampled 
and analyzed by itself, it will be seen that the very moderate 
charge of four dollars for this service will add ten cents per ton 
to the price of coal. This is probably 10 per cent, of the cost 
of the coal at the mouth of the mine and is an expense which is 
hardly justifiable. 

However if the test is worth making at all it must be on a 
sample which has fair claim to representativeness. The coal 
sampler stands eternally between the devil of inadequateness 
and the deep sea of excessive cost. In a few large plants where 
the coal is immediately crushed and removed to storage bins by 
conveyors a representative sample may readily be obtained. In 
most cases, however, the coal must be sampled as it comes from 
the car and the problem is more difficult. 

To many people coal is black and all that is black is coal. 
The more careful observer may detect bits of slate, and streaks 
or nodules of the brassy looking pyrites. The chemist knows 
that in addition the fine particles which have crushed because of 
their greater friability differ in composition from the lump coal 
and are usually higher in ash, though sometimes the reverse is 
the case, and that coal is far from being a mass of uniform 
composition. 

181 



182 GAS AND FUEL ANALYSIS 

Difference in Composition of Lump and Fine Coal 

The following tests taken from the author's record of coopera- 
tive tests undertaken jointly by the University of Michigan Gas 
Experiment Station and the United States Bureau of Mines to 
determine the availability of various coals for gas manufacture 
show some interesting variations. The coals had mostly been 
shipped in a small lots in sacks and were therefore considerably 
crushed in transit. They were screened in lots of about 600 lb. 
on a 3/4-in. bar screen preparatory to gas tests and the screenings 
and lump coal separately sampled. 

The sampling of the fine coal presented no difficulty since it 
was already in small lumps and could be crushed as fine as de- 
sired. The lump coal could not be finely crushed without 
detriment to the gas tests and so it was sampled by breaking 
the large lumps and then taking about two scoopfuls which were 
crushed and sampled as usual. Of the eleven coals tested in 
this manner four, one each from West Virginia, Colorado, New 
Mexico and Wyoming showed very little difference between the 
lumps and screenings. One coal showed decidedly less ash in 
the screenings than in the lump coal. Six coals showed notice- 
able and in some cases notable increases of ash and sulphur in 
screenings with corresponding decreases of heating value, as 
shown by the following analyses of the coals calculated to a dry 
basis. 

In the coal from Hellier, Kentucky for which there are three 
tests, the average heating value of the screenings is 1080 B.t.u. 
lower than that of the lump. This is entirely due to difference in 
ash as shown by the figures for heating value figured to coal dry 
and free from ash, where the difference disappears, the average 
heating value of the screenings being only 6 B.t.u. below that of 
the lump. The same thing is true of the other coals of the list — 
the variation in heating value of lump and screenings disappears al- 
most completely when calculated to a moisture and ash-free basis. 

Sulphur is never lower in the screenings than in the lump and 
is in some cases nearly twice as high. 

The last coal in the above table differs from all the others in 
that the screenings are much lower in ash than the lump. It 
might be thought that the sample had been labelled incorrectly 



SAMPLING COAL 



183 







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184 GAS AND FUEL ANALYSIS 

of it were not for the check afforded by analysis of the coke made 
from the lump coal. The coke contained 25.3 per cent, of ash, 
a figure which agrees well with the calculated result of 24.3 per 
cent. It is evident that in this coal the coal substance is the 
friable constituent while the ash forms a cementing material. 
The heating value of the dry screenings is 1366 B.t.u. higher 
than the lump, but when the ash is eliminated by calculation, 
the difference drops to 61 B.t.u. 

These figures show that the heating value of lump coal may 
vary as much as 2000 B.t.u. from that of fine coal and that 
usually the fine coal will contain more ash and have the lower 
heat value. Occasionally the reverse is the case. The true 
coal as reckoned to a moisture and ash free basis has practically 
the same heating value irrespective of its physical fineness. 

2. A Scoopful as a Sample. — It is commonly held that a 
few scoopfuls should be representative of a carload. This 
question was put to a practical test by Bailey 1 who had a lot 
of 3 tons of run-of-mine coal carted away in wheel barrows. 
As each barrow was filled a shovelful of coal was put into, 
not one, but into each of sixteen sample barrels. After the 
pile had disappeared there were left the sixteen sample barrels 
each with about 125 lb. of coal. These samples were crushed 
and " sampled carefully and the ash in each was determined. 
The results were as follows: 

Per cent, ash 

1 9.68 

2 10.28 

3 13 . 92 Maximum 

4 11.22 

5 10.88 

6 9.80 

7 11.84 

8 10.28 

9 10.10 

10 10.64 

11 10.06 

12 10.72 

13 9 . 46 Minimum 

14 ... 9.66 

15 ' 11.08 

16 11.34 

1 Trans. Am. Soc. Mech. Eng. } 27, 639 (1906). 



SAMPLING COAL 



185 



These samples which should have given results in close agree- 
ment show an extreme variation of 4.46 per cent, in their ash 
content. Had the heating values of these samples been deter- 
mined they would of course have shown similar discrepancies. 
If this coal has been sold on a premium and penalty basis and 
the coal with the average ash content of 10.68 would have 
been accepted without premium or penalty, the penalty on a 
basis of sample. No. 3 might readily have been six or eight 
cents per ton. And yet in this test the sample consisted of 
four or five shovelfuls taken from a lot as small as 3 tons and 
not from a whole car load. 

3. Influence of Lumps of Slate. — It is manifest that if all 
the ash of coal were to be concentrated in lumps the size of a 
football, that a single scoopful of coal would either show no 
ash or else an exorbitantly high amount. The error would 
be much less if the ash were in lumps only the size of walnuts 
and still less if it were more finely divided. Even if the ash 
were in large pieces if a sufficient number of scoops should be 
taken for analysis an average of all the figures would give a 
correct result. Bailey 1 gives the following table derived partly 
experimentally and partly mathematically showing the relation 
between the size of the largest piece of slate and the weight of 
the sample which must be taken in order that error in sampling 
shall not cause an error of over 1 per cent, in the ash. 



Size of slate, 


Wt. largest piece of 


Original sample should 


inches 


slate, pounds 


weigh, pounds 


4 


6.7 


39,000 


3 


2.5 


12,500 


2 


0.75 


3,800 


1 


0.12 


600 


0.75 


0.046 


230 


0.50 


0.018 


90 



Since there are very few shipments of coal other than the 
small sizes of anthracite which may not contain pieces of slate 
weighing a pound it is evident that on this basis a sample of 
less than 2 tons cannot be considered representative. Any 
smaller sample whether it be drawn from a wagon load or a 

1 Jour. Ind. and Eng. Chem., 1, 176 (1909). 



186 GAS AND FUEL ANALYSIS 

train of cars cannot be considered as representative of anything 
except itself. 

4. Taking a Sample. — It is fatal for a sampler to try and 
pick an average sample by taking what seems to him a fair 
proportion of coarse and fine, and rejecting material that looks 
either exceptionally good or bad. The only way is to determine 
how a most representative sample may be secured in a reasonable 
manner and then to carry out the operation. as mechanically 
as possible. 

If the sample is being taken from a wagon the shovel should 
be run along the bottom of the wagon after enough has been 
unloaded to allow the coal to assume its natural slope. The 
same procedure may be followed when coal is being shovelled 
from flat-bottomed cars. Where cars or wagons are being 
dumped the scoop may be held in the stream of falling coal. 
If cars are to be sampled before unloading, a trench, or better 
two trenches, each 12 in. deep should be dug across the car in 
order to remove excess of dust and cinder as well as snow which 
may have collected in the top layers. The sample is to be 
taken from the bottom of the trench. It is evident that coal 
sampled in this way will contain too small a proportion of fine 
coal, most of which will have sifted to the floor of the car. It 
is therefore preferable to sample during unloading. 

If it is necessarjr to determine the moisture in a car of coal 
which arrives wet or covered with ice the problem of sampling 
becomes even more complex. Fortunately, specifications are 
usually based on dry or air-dry coal so that the accidental 
moisture acquired in transit is not usually of importance. 

5. Mine Sampling. — The methods of sampling coal in a mine 
as recommended by the U. S. Bureau of Mines have been fully 
described by Holmes. 1 He recommends that for mines shipping 
200 tons or less daily, at least four samples should be taken. 
In general only clean, fresh coal should be taken and weathered 
coal should be avoided. Before cutting a sample the face of the 
bed and the roof is to be cleaned of loose fragments which 
might drop into the sample and a band 1 ft. wide extending 
from floor to roof is to be cut back at least an inch to expose 
fresh coal. The sample as cut from this prepared face should 

1 Technical Paper 1, Bureau of Mines, 1911. 



SAMPLING COAL 187 

include everything which the miner includes in the coal pre- 
pared for the market and should exclude the thick partings and 
large lenses of pyrite which are thrown out by the miner. The 
cut should be made perpendicularly about 2 in. deep and 6 in. 
wide so that there will be about 6 lb. of coal chips for each foot 
of thickness of the vein. These chips are to be caught on 
the waterproof sample blanket and crushed to pass a 1/2-in. 
screen. The sample is then quartered down and placed in 
a tight sample can. All the operations are to be carried 
on in the mine so as not to expose the coal to the outside 
atmosphere. 

6. Preparation of Sample. — The initial sample must be crushed 
and subdivided until it is finally ready for the chemical analysis. 
Care must be taken that it does not change during this process. 
It is almost impossible to prevent the moisture from changing 
and where it is necessary to deteimine this, the whole sample 
is usually weighed and allowed to dry in a warm room until 
it has become approximately air-dry, when it is again weighed. 
It is in any case difficult to sample coal which is very wet or 
covered with ice and a preliminary air-drying is, where possible, 
alway advisable. The sample must now be crushed and sub- 
divided. Bailey, in the reference already cited, gives the 
following rules for subdivision: 

Weight of sample to be Should be broken 

divided, pounds to inches 

7500 2 

3800 1.5 

1200 1 

460 0.75 

180 0.5 

40 2 mesh 

5 4 mesh . 

0.5 8 mesh 

0.25 10 mesh 

Where a well-equipped sampling laboratory is available 
the crushing will of course be easily accomplished by crushers 
and the subdivisions either made by mechanical samplers 
or upon clean iron plates. In such cases there is very little 
liability to error in this stage of the process. In many cases, 



188 GAS AND FUEL ANALYSIS 

however, the crushing and subdivisions must be carried out 
by hand, often on the floor of the boiler room and frequently 
under even less favorable conditions. The first requisite is 
cleanliness of the sampling surface. It is always preferable to 
sample on a metal plate. A cement floor is to be looked upon 
with suspicion and not to be used unless it is hard and fails 
to yield appreciable sand on vigorous sweeping. The liability 
to error is not great while the sample is large. When it becomes 
small enough it should be placed on oil cloth if a metal plate 
is not available. 

When working with a large sample the lumps may be crushed 
by a hammer or stamp to the size indicated and the material 
shovelled up, one shovelful out of every four going to the 
sampling barrow. All the coal should be shovelled away in 
this manner and the floor swept clean. It is not sufficient to 
shovel into the sampling barrow approximately one-fourth 
of the sample pile and leave the other three-fourths behind, for 
this process might include in the sample all the fine pieces 
resulting from one large piece of slate. When the sample 
has been reduced to 400 or 500 lb. it is customary after crushing 
to shovel the coal into a cone which is shovelled out again into a 
ring, care being taken to distribute the coal on the ring with a 
circular motion in order to distribute the fine pieces resulting 
from one large piece of slate. This ring is again to be shovelled 
into a cone, the sampler going round and round the ring and 
placing each shovelful of coal on the apex of the cone so that 
it may run down as nearly evenly as possible around the cir- 
cumference. The dust which cannot be shovelled up is then 
swept radially to the cone, the cone is flattened and cut into 
quarters by the shovel. The whole of one quarter including 
the sweepings is then shovelled into a tight barrow or bucket, 
the sampling floor is cleared and the process repeated until the 
sample is sufficiently reduced. The final sample should weigh 
4 or 5 lb. and be crushed to 1/8-in. size. It should at once be 
placed in a tight bottle or can and plainly labelled. 

7. Preservation of Sample. — If the percentage of moisture 
in the coal is of importance the sample should be placed in an 
air-tight receptacle and kept in a cool place. Coal which is 
not finely powdered does not change rapidly but it is advisable 



SAMPLING COAL 



189 



to have the analysis made promptly. Porter and Ovitz 1 have 
shown that samples of coal evolve methane and carbon 
dioxide and absorb oxygen for a period of several months. 
The changes due to the evolution of methane seldom rise above 
one-tenth of 1 per cent. The changes due to addition of oxygen 
are less certain but would seem to be possibly as high as 1/2 per 
cent. Parr has shown that Illinois coals may lose in heat value 
from 1/2 to 1 per cent, in the first ten days after mining and 
during the process of preparing the sample for analysis. The 
rapid changes take place soon after the coal is mined and the 
rate of change has usually materially decreased before the coal 
is sampled by the consumer. 

8. Usual Accuracy of Sampling. — The figures given by Bailey 
show that an accuracy of 1 per cent, in the ash is not to be ex- 
pected by ordinary methods. The following tables give some 
data resulting from the sampling of two separate carloads of 
coal. Four separate samples were taken from each car after 
loading at the mine by an inspector of the Bureau of Mines. The 
cars on arrival were sampled especially carefully, one-sixth of each 
carload being systematically separated as it was unloaded for the 
initial sample. This initial sample was cut into four separate ones 
which were separately sampled and analyzed. There are eight 
different samples from each carload whose analyses are tabulated 
in the accompanying table. 





PITTSBURG COAL, A. 


A. 15 








Air-dried coal 


B.t.u. of coal 
free from mois- 




Moisture 


Ash | S 


B.t.u. 


ture and ash 


Car at mine 


No. 1... 


0.95 


6.27 


0.91 


14213 


15319 




No. 2... 


1.00 


5.55 


0.72 


14315 


15318 




No. 3... 


0.98 


6.23 


0.98 


14182 


15284 




No. 4... 


0.96 


6.91 


0.84 


14107 


15295 




Average 


0.97 


6.24 


0.86 


14204 


15304 


Car as un- 


No. 1... 


1.11 


5.99 


0.82 


14215 


15301 


loaded 


No. 2... 


0.97 


6.54 


0.93 


14137 


15284 




No. 3... 


1.01 


5.63 


0.80 


14285 


15300 




No. 4... 


1.08 


5.88 


0.81 


14206 


15269 




Average 


1.04 


6.00 


0.84 


14211 


15288 



1 Technical Paper 2, Bureau of Mines, 1911. 



190 



GAS AND FUEL ANALYSIS 





FAIRMONT COAL, A. 


A. 16 








Air-dried coal 


B.t.u. of coal 
free from mois- 




Moisture 


Ash 


S 


B.t.u. 


ture and ash 


Car at mine. 


No. 1... 


1.10 


7.62 


0.67 


13925 


15255 




No. 2... 


1.10 


7.71 


0.64 


13874 


15216 




No. 3... 


1.07 


9.23 


0.83 


13678 


15240 




No. 4... 


1.17 


6.20 


0.52 


14096 


15217 




Average 


1.11 


7.69 


0.66 


13898 


15232 


Car as un- 


No. 1... 


1.24 


8.87 


0.64 


13671 


15209 


loaded 


No. 2... 


1.21 


8.98 


0.69 


13640 


15188 




No. 3... 


1.28 


8.89 


0.69 


13638 


15182 




No. 4... 


1.27 


9.06 


0.73 


13604 


15160 




Average 


1.24 


8.95 


0.69 


13638 


15185 



The chief variable in these samples is the ash which in turn 
affects the heating value. The accuracy of the analyses is at- 
tested by the close agreement of the heating value referred to coal 
dry and free from ash. In the Fairmont coal the heating value 
of the coal taken at the mine is noticeably higher than that sam- 
pled from the car, when calculated to an ash and moisture free 
basis, due possibly to escape of gas from the freshly mined coal. 

The average ash content of the Pittsburgh coal is closely the 
same in the two sets but in the Fairmont coal the average ash 
as sampled from the car at the mine was 1.6 per cent, lower than 
that obtained as the car was unloaded. As was pointed out 
above, this variation is a normal one due to the method of sam- 
pling. The variation in the average heating value of these two 
series amounts to 260 B.t.u., a figure which might easily cause 
a difference in price of five cents a ton. 

Turning from averages to individual figures we find a better 
agreement with the Pittsburgh than the Fairmont coal, and in 
each series the agreement better between the samples taken from 
the car as unloaded, as should have been the case The extremes 
for the Fairmont coal are tabulated as follows : 





Low ash 


High ash 


Difference 




per cent, ash B.t.u. 


per cent, ash | B.t.u. 


per cent, ash B.t.u. 


Car at mine 

Car as unloaded . 


6.20 

8.87 


14096 
13671" 


9.23 
9.06 


13678 
13604 


3.03 1 418 
0.19 69 



The agreement between the samples taken very carefully 



SAMPLING COAL 



191 



from the car as unloaded is excellent. The difference between 
the extremes of the samples taken from the loaded car which 
amounts to 426 B.t.u. might readily cause a difference of nine 
cents a ton on the settlement price of the coal. 

The engineers of the U. S. Bureau of Mines 1 have studied the 
error in sampling on ten different lots of coal. Each of two in- 
spectors collected a sample of 100 lb. from a given lot of coal. In 
lot a their samples differed in heating value by 158 B.t.u. per 
pound of dry coal. They then each collected a second sample 
of 100 lb. and averaged the results of this with their first sample. 
The difference between the two collectors than dropped to 132 
B.t.u. In the same way they continued to take successive samples 
of 100 lb. and average all of their results and after ten of such 
samples had been taken the differences between the averages 
for each man was small. As the result of tests on ten different 
lots of coal they found that it was necessary to collect and average 
seven different samples of 100 lb. each in order that the results 
obtained by two collectors should not differ by more than 50 
B.t.u. Their average results are given in the following table. 

AVERAGE ERROR IN SAMPLING 10 LOTS OF COAL AS SHOWN 
BY THE DISAGREEMENT IN HEATING VALUE OF SUC- 
CESSIVE SAMPLES TAKEN BY TWO COLLECTORS 





Disagreement between two 

collectors in B.t.u. per 

pound dry coal 


First sample of 100 lb 


251 


Average of 2 samples of 100 lb 


200 


Average of 3 samples of 100 lb 


125 


Average, of 4 samples of 100 lb 


111 


Average of 5 samples of 100 lb 


75 


Average of 6 samples of 100 lb 


78 


Average of 7 samples of 100 lb 


51 


Average of 8 samples of 100 lb 


53 


Average of 9 samples of 100 lb 


44 


Average of 10 samples of 100 lb 


37 


Average of 11 samples of 100 lb 


32 


Average of 12 samples of 100 lb. . 


32 


Average of 13 samples of 100 lb 


25 







9. Standard Methods of Sampling. 

1 Bui. 63, Bureau of Mines. 



-A committee of the 



192 GAS AND FUEL ANALYSIS 

American Society for Testing Materials has recommended a 
standard method of sampling which is to be found in the Pro- 
ceedings of the Society for 1915. In the same volume is a 
standard method for sampling coke. 

The Bureau of Mines recommends that the gross sample collected 
be never less than 1000 lb. In sampling cargo deliveries of 5000 
and more tons the recommendation is that the sample be from 
4000 to 5000 lb. and that the sample be crushed in approximately 
500-lb. lots from each of which a sample is sent to the laboratory. 
Four or five analyses are usually made for each cargo and the 
results are averaged. Detailed directions for sampling and also 
specifications for coal as used by the Government are given in 
Bulletin 63 of the Bureau of Mines entitled Sampling Coal Deliv- 
eries and Types of Government Specifications for the Purchase of 
Coal by George S. Pope. Copies may be obtained from the 
Director of the Bureau of Mines in Washington. 

10. Reliability of Samples. — It is evident from the preceding 
paragraphs that it is possible to sample crushed coal with fair 
accuracy, but that it is not possible to accurately sample coal 
containing large lumps without greater expense than is usually 
warranted. The error is largely an accidental one due to the 
inclusion or rejection of too many or too few of the larger pieces 
of slate in the sample. There may also be a systematic error if 
care has not been taken to get a proper proportion of coarse and 
fine coal. So far as the error is accidental, it will diminish, ac- 
cording to the law of probabilities, with increasing number of 
samples, so that although any one sample may be in error by 3 
per cent., the average of fifty samples should be quite accurate. 
Contracts which involve the delivery of coal throughout the year 
may therefore be equitably settled on a sliding scale based on 
analysis, for the undue premium on one shipment will be counter- 
balanced by the undue penalty on another and in the course of 
a year a fair average will have been reached. If it is necessary to 
determine accurately the value of a single shipment, greater care 
and expense is necessary than the sum at issue will usually 
warrant. 



CHAPTER XV 
THE CHEMICAL ANALYSIS OF COAL 

1. Introduction. — The methods used in analysis of coal may 
be grouped into two main divisions. In ultimate analysis the 
aim is to report as accurately as may be the percentages of the 
chemical elements, especially carbon, hydrogen, nitrogen, oxygen 
and sulphur. These elements are reported as elements without 
any attempt to indicate the manner in which they are combined 
in the coal. This method of analysis is scientifically valuable but 
finds few applications in technical work. In proximate analysis, 
on the other hand, the attempt is made to group the constituents 
of the coal according to certain physical properties which are 
technically important such as moisture, volatile matter and ash. 
This method of analysis is of great commercial importance. 
These two methods of analysis are applicable to all forms of 
solid and liquid fuel — peat, lignite, bituminous coal, anthracite, 
coke, petroleum, tar, etc. — with slight modifications required by 
the physical properties of the fuel being investigated. 

2. Proximate Analysis. — The usual items included in a proxi- 
mate analysis are moisture, volatile matter, fixed carbon and ash. 
Sulphur is frequently included in the report, but is determined 
separately. There is no difficulty in comprehending what is 
meant by the terms moisture and ash. The expressions volatile 
matter and fixed carbon require explanation, for they are merely 
relative terms which can be interpreted only by reference to 
certain definite conditions of analysis. If coal be heated to red- 
ness the heat will decompose a portion of the coal substance. 
Part of this decomposed coal will be evolved as a thick black 
smoke which will burn in the air and part will remain behind 
as a solid coke or carbonaceous reside. If tar or petroleum 
be treated in this manner part of the substance will be 
driven off in the same form in which it existed in the oil. In 
the case of coal the material volatilized is formed only 
through the decomposing action of the heat. In proximate 

13 193 



194 GAS AND FUEL ANALYSIS 

analysis no attempt is made to separate these two classes of 
products. Everything which is evolved in the process is called 
" volatile." The residue remaining in the crucible after this 
process consists of ash and a material which is largely carbon 
and which forms the so-called "fixed carbon." The percentages 
reported as volatile matter and fixed carbon will vary with 
every modification of the conditions of analysis. The mois- 
ture and ash are also liable to vary with change in detail of 
method. It is therefore very important that all chemists use 
the same method in order that their results may be comparable. 
In 1899 1 a committee of the American Chemical Society which had 
made a careful study of the subject reported a scheme of analysis 
which has been generally recognized as standard for the United 
States. In 1910 a joint committee of the American Chemical 
Society and the American Society for Testing Materials was 
formed to consider a revision of these methods, and their sugges- 
tions as embodied in their preliminary report 2 are included in 
this chapter. 

3. Preliminary Examination of Sample. — In the preceding 
chapter on Sampling the precautions to be observed in taking 
the initial sample and in subdividing it were discussed. There is 
no definite point where the sampler is to stop in his process of 
subdivision and turn the material over to the chemist, but since 
the sampler is in general a field worker it is customary to consider 
his work as ended when the sample has been reduced in weight 
sufficiently to allow its easy transportation to the laboratory. 
Sometimes it is stated that the sample sent to the laboratory 
should weigh from 3 to 5 lb. 

The chemist receiving a sample should note the nature of the 
package as well as its marks. Coal shipped in a canvas sack or a 
paper carton which is not tight will almost certainly have changed 
in moisture content and will probably have lost some of its finer 
particles. After opening the package the net weight of sample 
and an at least approximate estimate of its physical condition 
should be recorded. Information as to whether the sample as 
received was wet or dry and whether it showed evident pieces 
of slate or pyrite is sometimes of importance. The size of the 

1 Jour. Am. Chem. Soc, 21, 1116 (1899). 
* Jour. Jnd, and Eng, Chem., 5, 517 (1913). 



THE CHEMICAL ANALYSIS OF COAL 195 

largest lumps relative to the size of the sample shipped will give 
some indication of the care which has been used in the preparation 
of the sample. The chemist should, for his own protection, state 
in his report when the sample is manifestly a non-representative 
one, and when insufficient care has been exercised in packing it 
for shipment. 

The 1913 report of the Committee on Coal Analysis recommends 
that the size of sample to be transmitted to the laboratory vary 
with the size of the coal as follows : 

Size of largest impurities Minimum weight of sample 



1/2 in 

3/8 in ■; 

1/4 in 

3/16 to 1/5 in. = 4 mesh, 
1/8 in 



75 1b. 
30 1b. 

9 1b. 

5 1b. 
3 to 5 lb. 



4. Air-drying. — It is inconvenient to handle samples of coal 
which are wet, since they clog the mills and cannot be mixed 
readily. They also change in weight rapidly in the air. It is 
therefore standard practice to air-dry the sample. This may be 
accomplished by spreading in a thin layer in a tin pan placed in 
a warm room for twenty-four hours or longer if necessary to 
bring it to approximately constant weight. The process may be 
hastened by placing the samples in an oven such as is used 
at the Bureau of Mines 1 which is heated to not over 100° F. and 
which is provided with forced ventilation. In this oven, which is 
illustrated in Fig. 41, air is heated by a Bunsen burner and circu- 
lated by a small electric fan. The loss in weight during this 
process is reported as air-drying loss. All analyses are made on 
this air-dried coal since it may be weighed and handled in the air 
with relatively slight change of weight. There is evidence that 
the coal slowly changes in this air-drying process, so that it should 
no tbe exposed to the air longer than necessary. Porter 2 reports 
that Pittsburg coal on drying eight days at 35° C. absorbed 0.17 
per cent, of oxygen and that a Wyoming coal similarly treated 
absorbed 0.70 per cent. 



1 Technical Paper 8, Bureau of Mines, 1912. 

2 Jour. Ind. and Eng. Chem., 5, 520 (1913). 



196 



GAS AND FUEL ANALYSIS 



5. Grinding and Preserving the Sample for Analysis. — The 

sample of coal which has been air-dried or is at least so nearly 
air-dry that it does not change in weight in the air rapidly is to 
be crushed and subdivided until a portion of 50 or 60 grm. is 
obtained from which a sample of 1 grm. may be taken which 




iH 4'4" -A 

Fig. 41. — Oven for air-drying coal samples. 

shall be representative of the whole original mass of coal. Bailey 
in the reference quoted in the preceding chapter gives the follow- 
ing rules for subdivision in the laboratory. 



Size of coal mesh 


Should not be divided to 
less than 


2 

4 

8 

10 

20 


8300 grm. 

1100 grm. 

120 grm. 

55 grm. 

3 grm. 



THE CHEMICAL ANALYSIS OF COAL 197 

He recommends that as soon as the sample has been put through 
an 8-mesh sieve that it be all crushed to 60-mesh or finer. 

The crushing to 12-mesh may be done by hand in a mortar or 
in any type of crusher without much danger of injuring the 
sample if it is done rapidly. It is necessary to take precautions, 
however, to prevent injury to the sample during fine grinding, 
for finely ground coal absorbs oxygen from the air rapidly and 
gives off water. The exact nature of this reaction is not un- 
derstood but it is known to sensibly affect the heating value. 
This change is accelerated if the sample becomes heated during 
the fine grinding. For this reason disc grinders should be used 
with great caution. They grind rapidly but the plates get hot, 
sometimes hot enough to start destructive distillation of the 
coal, which manifests itself by a tarry odor. If the disc grinder 
is used the plates must not be set closer than necessary and the 
coal must be fed very slowly. The best method of finely 
grinding coal is to use a jar mill. This consists of a heavy 
porcelain jar provided with a cover which may be clamped 
tight on a rubber gasket. It is filled about one-third full of 
round flint pebbles or porcelain balls and is placed in a frame 
where it may be rotated at the rate of 50 to 75 revolutions 
per minute. The balls tumbling over each other fall with suffi- 
cient force to crack the small pieces of coal, but are themselves 
worn off to only a negligible extent. The longer the coal is 
left in the jar the finer it becomes and it is easy to get any desired 
degree of fineness. The size of the jar required and the diameter 
of the pebbles will vary with the hardness of the material and the 
size of the lumps. If the lumps have a diameter even as great as 
one-fourth that of the pebbles, some of the lumps may become 
simply rounded balls themselves and not be crushed by the im- 
pact of the pebbles. If the coal has been put through a 10- or 12- 
mesh sieve before going into the ball mill a jar of 8 in. internal 
diameter and with pebbles 3/4 in. or 1 in. in diameter will grind 
the sample properly, provided the coal does not occupy over one- 
sixth of the volume of the jar. When the grinding is completed 
the jar is emptied onto a coarse sieve which retains the balls. 
The coal should be tested on a 60-mesh sieve and any portions 
failing to pass it should be separately ground to pass an 80-mesh 
sieve and added to the main portion. These coarse particles 



198 GAS AND FUEL ANALYSIS 

are liable to be slate or pyrites and therefore especial care must 
be taken to see that they are finely ground and mixed with the 
main sample. A coal ground to pass a 60-mesh sieve is fine 
enough to make a 1-grm. sample as representative of the lot as 
the various intermediate samples were of the initial sample. It 
is not desirable to grind the coal much finer because of the 
increased error due to loss of moisture and absorption of oxygen 
by the finely powdered coal. 

This finely ground sample may now be stored as a whole in 
a fruit jar or subdivided and an amount of only 50 grm. placed 
in a wide-mouthed bottle closed with a rubber stopper. The 
bottle should be filled only half full so that the analyst before 
weighing out his sample may gently shake and rotate the bottle 
to mix the contents. Pyrites and slate tend to work to the 
bottom of a sample bottle and the precaution of mixing before 
taking a sample should never be omitted. 

Even the most carefully preserved coals deteriorate in time. 
Parr 1 has shown that in three years' storage in the laboratory 
Eastern coals lose in heating value to the extent of 0.5 to 1.5 
per cent., while Illinois coals deteriorate to the extent of 3 to 5 
per cent. Coals which are to be kept for a long period should 
be sealed as nearly air-tight as possible. 

6. Moisture. — The determination of moisture in coals is 
complicated by the change which the coal substance itself 
undergoes when subjected to heat and exposure to the air. 
The method recommended by the committee of the American 
Chemical Society in 1899 prescribes that 1 grm. of the coal 
shall be dried in an open porcelain or platinum crucible at 
104-107° C. for one hour and shall then be cooled in a desiccator 
and weighed covered. 

The errors in the determination of moisture in coal have been 
studied by several investigators, among them Hillebrand and 
Badger 2 at the Bureau of Standards. They conclude that the 
most nearly correct results may be obtained by drying in vacuo 
over concentrated sulphuric acid for a period of two days or 
more. The method prescribed above of heating for one hour 
in a closed oven at 105°-110° C. showed the moisture to be 

1 Eighth Internat. Congr. Appl. Chem., 10, 225 (1912). 

2 Eighth Internat. Congr. Appl. Chem., 10, 187. (1912). 



THE CHEMICAL ANALYSIS OF COAL 199 

roughly nine-tenths as great as that obtained by the vacuum 
method when the comparisons were made on coals which had 
not been unduly weathered. If the heating in the oven was 
prolonged an hour longer the apparent moisture rose somewhat, 
but was still below that obtained by the vacuum method. If 
the coal was heated for one hour in an oven through which 
dry air was circulated, the results obtained were much more 
consistent and in most cases approached quite closely those 
obtained in a vacuum. 

The method adopted as standard by the U. S. Bureau of 
Mines, as given in their Technical Paper 8, is to take a 1-grm. 
sample of the 60-mesh coal, place it in a weighed 7/8 in. by 1 3/4 
in. porcelain crucible and heat for an hour at 105° C. in a constant 
temperature oven in a stream of dry air. The crucible is then 
removed from the oven, covered and cooled in a desiccator 
over sulphuric acid. The loss in weight multiplied by 100 
is counted as the percentage of moisture. The oven which they 
use is of copper with double walls. The space between the 
inner and outer wall is filled with a solution of approximately- 
45 parts by weight of glycerine and 55 of water, the exact 
proportions being modified to get a solution boiling at 105° C. 
A reflux condenser prevents change in boiling-point through 
evaporation of the water. A current of air dried by passing 
through sulphuric acid and preheated by passing through a 
copper spiral immersed in the glycerine is forced into the drying 
chamber at the back and escapes through a small hole in the 
door. The air is blown in at a rate sufficient to change the 
volume of air in the oven from 8 to 10 times an hour. 

The 1913 report of the Committee on Coal Analysis recom- 
mends that the sample of approximately 1 grm. be weighed 
into a pair of shallow weighing capsules with ground caps. 
For anthracite and bituminous coals the capsules are to be 
placed open in a preheated oven at 104-110° C, through which 
passes a current of air dried by concentrated sulphuric acid. 
After being heated for one hour in this oven the capsules are 
to be removed, covered at once and cooled in a desiccator con- 
taining concentrated sulphuric acid. Sub-bituminous and lig- 
nitic coals are to be dried in a stream of dry carbon dioxide or 
nitrogen. After the samples are dried they are to be placed in a 



200 GAS AND FUEL ANALYSIS 

vacuum desiccator which is then exhausted to remove absorbed 
carbon dioxide. After exhaustion the desiccator is refilled with 
dry air. 

7. Volatile Matter. — There can never be an absolute method 
for the determination of volatile matter, for only a very small 
proportion of the material evolved from coal at a red heat 
was present as such in the coal. Most of this volatile ma- 
terial is a decomposition product whose amount varies with 
the rate of heating, the maximum temperature attained, the 
character of the flame, the size of the crucible and other condi- 
tions. It is necessary, therefore, in a standard method to 
fix every possible variable as rigidly as possible. 

The 1899 method of the American Chemical Society is as 
follows: 

"Place 1 grm. of fresh, undried, powdered coal in a platinum cruci- 
ble, weighing 20 or 30 grm. and having a tightly fitting cover. Heat 
over the full flame of a Bunsen burner for seven minutes. The cruci- 
ble should be supported on a platinum triangle with the bottom six to 
eight centimeters above the top of the burner. The flame should be 
fully twenty centimeters high when burning free, and the determina- 
tion should be made in a place free from draughts. The upper surface 
should remain covered with carbon. To find 'Volatile Combustible 
Matter' substract the per cent, of moisture from the loss found here." 

More recent investigations especially by Fieldner and Davis 1 
and by Parr 2 have thrown some light on the causes of variation. 
The former authors working in the laboratories of the U. S. 
Bureau of Mines at Pittsburgh and Washington found that the 
carburetted water gas of Washington gave a maximum tempera- 
ture of 970° C. within the crucible which was 120° hotter than 
could be obtained with the coal gas of Pittsburgh or with natural 
gas burned under favorable conditions. They summarize the 
results of their experiments as follows: 

"Two laboratories are likely to vary 2 per cent, in volatile matter, 
both using the official method (of 1899). The percentage of volatile 
matter obtained from the same sample of coal varies with the tem- 
perature and rate of heating. This is not sufficiently defined by height 

1 Jour. Ind. and Eng. Chem., 2, 304 (1910). 

2 Jour. Ind. and Eng. Chem., 3, 900 (1911). 



THE CHEMICAL ANALYSIS OF COAL 201 

of flame. Temperatures ranging from 760° C. to 890° C. may be at- 
tained with a 20-cm. natural gas flame, when the gas pressure is varied 
from 1 to 13 in. of water; variations of 2 per cent, volatile matter are 
thus produced. Differences in type and sizes of burner influence re- 
sults from 0.3 to 1.5 per cent. Polished crucibles become hotter and 
yield about 1 per cent, more volatile matter than dull gray ones. Labo- 
ratories using natural gas are apt to get results on volatile matter that 
are considerably lower than those using coal gas, unless the following 
precautions are observed: (1) Gas should be supplied to the burner 
at a pressure of not less than 10 in. of water. (2) Natural gas burners 
admitting an ample supply of air should be used. (3) Gas and air 
should be regulated so that a flame with a short, well-defined inner 
cone is produced. (4) The crucibles should be supported on platinum 
triangles and kept in well-polished condition." 

The 1913 report of the Committee on Coal Analysis recom- 
mends the following two alternate methods for the determination 
of volatile matter. 

"It is recommended that for volatile matter determinations a 10- 
grm. platinum crucible be used having a capsule cover, that is, one which 
fits inside of the crucible and not on top. The crucible with 1 grm. of 
coal is placed in a muffle maintained at approximately 950° C. for seven 
minutes. With a muffle of the horizontal type, the crucible should not 
rest on the floor of the muffle but should be supported on a platinum 
or nichrome triangle bent into a tripod form. After the more rapid 
discharge of the volatile matter, well shown by the disappearance of 
the luminous flame, the cover should be tapped lightly to more per- 
fectly seal the cover and thus guard against the admission of air. 

"One gram of coal is placed in a platinum crucible of approximately 
20 c.c. capacity (35 mm. in diameter at the top and 35 mm. high). 
The crucible should have a capsule cover which will readily adjust 
itself to the inside upper surface of the crucible., The crucible is placed 
in the flame of a Meker burner, size No. 4, having approximately an 
outside diameter at the top of 25 mm. and giving a flame not less than 
15 cm. high. The temperature should be from 900° to 950° C. de- 
termined by placing a thermocouple through the perforated cover which 
for this purpose may be of nickel. The junction of the couple should 
be placed in contact with the center of the bottom of the crucible. 
Or the temperature may be indicated by the fusion of pure potassium 
chromate in the covered crucible (fusion of K 2 Cr0 4 , 940° C.). The 
crucible is placed in the flame about 1 cm. above the top of the burner 
and the heating is continued for seven minutes. After the main part 



202 GAS AND FUEL ANALYSIS 

of the gases have been discharged the cover should be tapped into place 
as above described. 

"For lignites a preliminary heating of five minutes is carried out, 
during which time the flame of the burner is played upon the bottom 
of the crucible in such a manner as to bring about the discharge of vola- 
tile matter at a rate not sufficient to cause sparking. After the pre- 
liminary heating the crucible is placed in the full burner flame for 
seven minutes as above described." 

8. Ash. — The ash of coal is generally defined as the mineral 
residue remaining after complete combustion. The 1899 method 
of the American Chemical Society is as follows: 

"Burn the portion of powdered coal used for the determination of 
moisture, at first over a very low flame, with the crucible open and in- 
clined, till free from carbon. If properly treated, this sample can be 
burned much more quickly than the dense carbon left from the de- 
termination of volatile matter. It is advisable to examine the ash for 
unburned carbon by moistening it with alcohol." 

The errors attending the determination of ash have been 
studied very carefully by Parr 1 , who has shown that 90 per cent, 
of the Illinois coals carry as much as 0.2 per cent, of calcium car- 
bonate, nearly half have more than 1 per cent., one-fifth have 
more than 2 per cent., a considerable number over 4 per cent., 
and a few isolated cases carry over 10 per cent, of calcium car- 
bonate in the raw coal. Since decomposition of CaO03 is rapid 
at 900° C. and evident at 600° it is apparent that in coals of this 
type care must be taken to determine the actual amount of 
CaCOs present. Parr has also shown that sulphate in the form 
of ferrous or ferric sulphate is present in fresh coal in amounts 
varying from a few tenths up to 1 per cent, and that this amount 
increases rapidly in the finely ground portions of the laboratory 
sample. With coals high in lime this sulphate on ignition for 
ash probably becomes calcium sulphate, as does also the sulphur 
of pyrites. 

The 1913 report of the Committee on Coal Analysis recom- 
mends the following method for the determination of ash. 

1 Jour. Ind. and Eng. Chem., 5, 523 (1913). 111. State Geological Survey, 
Bui. 16, p. 242. 



THE CHEMICAL ANALYSIS OF COAL 203 

"Unless the coal is of a type known to be free from carbonate the 
amount of carbon dioxide must be determine.d. A 5-grm. sample, 
recently boiled distilled water and dilute hydrochloric acid are em- 
ployed, making use of any convenient apparatus for collecting, absorb- 
ing and measuring accurately the carbon dioxide discharged from the 
coal. It is most convenient to obtain the factor as in the form of 
carbon. 

"One gram of coal, either freshly weighed or that which has been used 
for the moisture determination, is ignited in a shallow capsule or porce- 
lain crucible by placing directly in a muffle maintained at a dull or 
cherry-red temperature between 700 and 750° C. and retained at this 
temperature for 20 or 30 minutes or until all of the carbon is burned out. 
The capsule is cooled in a desiccator and weighed. In the absence of a 
muffle the desired temperature may be obtained by placing the capsule 
at first just above the tip of a Bunsen flame turned down to about 2 
or 3 in. in height. After the larger part of the carbon is burned off in 
this manner the flame is increased so that the tip comes well into 
contact with the bottom of the capsule. 

" For coals having carbon dioxide present in an amount to exceed 0.2 
per cent., the ash after cooling is moistened with a few drops of sulphuric 
acid (diluted 1 : 1) and again carefully brought up to 750° C. and re- 
tained at that temperature for three to five minutes. The capsule is 
cooled in a desicator and weighed. Three times the equivalent of 
carbon present as carbon dioxide is subtracted from the ash as weighed 
in order to restore the weight of the calcium sulphate formed to the 
equivalent of calcium carbonate." 

The appearance of the ash gives some indication of its fusing 
point and hence its tendency to form clinkers. The largest con- 
stituents in ash are silica and alumina, all of whose compounds 
have relatively high melting-point and are white in color. Iron 
oxide colors ash red and reduces the melting-point of the alumina 
silica series markedly. Therefore a red ash indicates low melting- 
point and trouble with clinker while a white ash indicates high 
melting-point. This rule fails with coals such as those from 
Illinois which carry material amounts of lime, for the lime reduces 
the melting-point without giving a color. However, the Illinois 
coals usually carry enough iron to give a red color as well. 

9. Fixed Carbon. — Fixed carbon is obtained by adding together 
the weights of moisture, volatile matter and ash and subtracting 
this sum from the weight of the initial sample. Since the amount 



204 GAS AND FUEL ANALYSIS 

of fixed carbon is obtained by difference, proximate analyses of 
coal always add up to an even 100 per cent. The percentage 
of fixed carbon plus ash gives a fair indication of the amount of 
coke which would be obtained from a coal. An indication of the 
quality of the coke may be obtained from an examination of the 
residue remaining after the determination of volatile matter. 
Good coking coals give a button of hard dense coke. Feebly 
coking coals give a cracked and weak button while non-coking 
anthracites and lignites give a powdery or granular residue. 

10. Sulphur. — The estimation of sulphur is usually considered 
as part of a proximate analysis although it is estimated separately 
and its percentage is not included in the 100 per cent, formed by 
the sum of the moisture, volatile matter, fixed carbon and ash. 
Sulphur usually exists in coal as pyrites FeS 2 , but part of it may 
exist in combination with carbon compounds, part even as free 
sulphur and especially in weathered coals as calcium sulphate 
or sulphate of iron. No attempt is ordinarily made to distinguish 
between these various forms of sulphur. The coal is treated 
with an agent which finally brings all forms of sulphur into a 
soluble sulphate form. This is then precipitated as barium sul- 
phate and calculated back to sulphur. The method recommended 
in 1899 by the American Chemical Society was a modification of 
that proposed by Eschka in 1874. 

The committee on Coal Analysis in its 1913 recommendations 
adopts the report presented by Barker 1 permitting the use of three 
alternative methods which have shown themselves to be accurate. 
The methods are: 

(a) the Eschka method. 

(6) the Atkinson method of fusion with sodium carbonate. 

(c) the method of fusion with sodium peroxide. 

The Eschka method is recommended in substantially the same 
form as in the standard method of 1899. The substitution of 
copper oxide for magnesium oxide in the method gives more 
rapid combustion but it has been objected to on the ground that 
the black specks of copper oxide look so much like free carbon 
that it is difficulty to tell when the coal is completely burned. 
The following details of the Eschka method are from the 
Committee's report. 

1 Jour. Ind. and Eng. Chem., 5, 524 (1913). 



THE CHEMICAL ANALYSIS OF COAL 205 

"The Eschka Method. — The essentials of this method as described 
by G. L. Heath 1 have been modified as given in the former report of 
the Committee of the American Chemical Society on Coal Analysis. 2 
Additional directions for application when city gas is used are also 
included in the method herein recommended. 

" Thoroughly mix on glazed paper 1.3737 grm. of coal and 6 grm. 
of Eschka mixture. This mixture is prepared by thoroughly incopor- 
ating two parts magnesium oxide with one part of sodium carbonate 
by passing through a 40-mesh screen. By this method of preparation 
the mixture attains a uniformity comparable with that of the labo- 
ratory sample of coal and thorough incorporation is, therefore, more 
easily effected. Transfer to a No. 1 Royal Berlin porcelain crucible 
and cover with about two grams of the Eschka mixture. On account 
of the amount of sulphur contained in artificial gas, it is preferable 
to heat the crucible over an alcohol, gasoline or natural gas flame or in 
an electrically heated muffle. Heat the crucible, placed in a slanting 
position on a triangle, over a very low flame to avoid rapid expulsion 
of the volatile matter, which tends to prevent complete absorption of 
the products of combustion of sulphur. Heat the crucible slowly for 
about 30 minutes, gradually increasing the temperature and occasionally 
stirring until all black particles disappear, which is an indication of the 
completeness of the procedure. 

"The use of artificial gas for heating the coal and Eschka mixture 
is permissible, provided the crucibles are heated in a muffle and a blank 
determination of the amount of sulphur absorbed from the gas is made. 
Place a crucible in a cold gas muffle and gradually raise the temperature 
to about 870° or 925° C. (cherry-red heat) in about one hour. Main- 
tain this maximum temperature for about one and a half hours and 
then allow the crucible to cool in the muffle. Remove and empty the 
contents into a 300 c.c. beaker and digest with 200 c.c. of hot water 
for one-half to three-quarters of an hour, with occasional stirring. 
Filter and wash the insoluble matter by decantation. After several 
washings in this manner, transfer the insoluble matter to the filter and 
wash five times, keeping the mixture well agitated. Treat the filtrate 
amounting to about 250 c.c. with 10 to 20 c.c. of saturated bromine 
water and make slightly acid with concentrated hydrochloric acid. 
Transfer the beakers to the hot plate and, upon boiling, precipitate 
the soluble sulphates by adding 'slowly from a pipet with constant stir- 
ring 10 c.c. of a hot 10 per cent, solution of barium chloride. Continue 
boiling for fifteen minutes and allow to stand for at least two hours 

1 /. Am. Chem. Soc, 20, 630. 

2 Ibid., 21, 1127. 



206 GAS AND FUEL ANALYSIS 

at a temperature just below boiling. Filter through an ashless filter 
paper and wash first with hot water containing 1 c.c. of hydrochloric 
acid per liter and then with hot distilled water until a silver nitrate 
solution shows no precipitate with a drop of the filtrate. Place the 
wet filter containing the precipitate of barium sulphate in a weighed 
platinum or alundum crucible, allowing a free access of air by folding 
the paper over the precipitate loosely to prevent spattering. The paper 
should be smoked off gradually at first. After the paper is practically 
consumed raise the temperature to approximately 925° C. and heat to 
constant weight. In case artificial gas is used as a heating agent, a 
blank to correct for contamination due to sulphur in the gas is carried 
through the process in the manner described above, using the same 
amounts of Eschka mixture, wash water, bromine water, hydrochloric 
acid and barium chloride solution as employed in the regular determina- 
tion. A large number of tests using a mixed coal and carburetted 
water gas containing not more than 25 grains of sulphur per 100 cu. ft. 
show blanks averaging 0.003 grm. of barium sulphate. These blanks 
include the impurities in the form of sulphur compounds in the reagents, 
which amount to nearly one-half of the total weights. The percentage 
of sulphur is obtained by deducting the blank, provided artificial gas 
is used, and multiplying the resulting figures by 10." 

The Peroxide Fusion Method. — The decomposition of coal 
by fusion with sodium peroxide was first proposed by Parr 1 
for calorimetric purposes. The reaction was adapted to the esti- 
mation of sulphur by Sundstrom 2 and later modified by Pennock 
and Morton 3 , and Parr 4 . The method is entirely reliable and 
is much more rapid than the Eschka method. 

When a mixture of a dry combustible substance and sodium 
peroxide in proper proportions is ignited by a hot iron wire, the 
mass fuses with very little spattering and the sulphur, no matter 
what its initial form of combination, is converted to a soluble 
sodium sulphate. If the coal is damp or the proportions are not 
correct there may be violent spattering so the reaction should 
be carried out in a closed vessel. The residue from the deter- 
mination of heating value in the Parr calorimeter is of course 
available at once for the estimation of sulphur. Where a separate 

1 J. Am. Chem. Soc, 22, 646 (1900). 

2 /. Am. Chem. Soc, 25, 184 (1903). 

3 J. Am. Chem. Soc. 25, 1265 (1903). 

4 J. Am. Chem. Soc, 30, 7G7 (1908). 



THE CHEMICAL ANALYSIS OF COAL 



207 



W////////////////////X/. 



combustion for sulphur is to be made a simple crucible of steel or 
brass provided with a perforated cover which may be clamped in 
place is used, as shown in Fig. 42. For a charge of 0.7 grm. 
bituminous coal about 16 grm. of sodium peroxide are required 
while for the same weight of coke or anthracite about 12 grm. of 
peroxide are best. The charge is mixed, the cover clamped on 
and the crucible placed on a support in a pan of water, so that 
its lower half is immersed and yet there is free circulation of water 
around the bottom. The charge is fired by a stiff iron wire which 
is heated to redness and thrust 
through the hole in the cover. If the 
reaction proceeds properly almost no 
flame will issue from the hole. If the 
proportions are not correct there may 
be considerable spattering so that the 
operator should stand at arms length 
from the crucible when inserting the 
wire. If the first explosion is too vio- 
lent, add more sodium peroxide which 
acts as a diluent. If, on the other 
hand, combustion has been incomplete 
as shown by soot on the inside of the 
lid of the crucible, decrease the amount 
of sodium peroxide on the next at- 
tempt. If there is difficulty in ob- 
taining ignition as is sometimes the case with coke and especially 
with ashes, add an accelerator. Parr recommends the following 
fusion mixture: 10 grm. sodium peroxide, 0.5 grm. potassium 
chlorate, 0.5 grm. benzoic acid. 

To dissolve the fused mass, place the crucible and cover 
in about 200 c.c. of distilled water. Rinse off the crucible, 
acidify slightly with HC1, filter out any insoluble matter and 
proceed with precipitation of BaS0 4 as in the Eschka method. 

The details of the Atkinson method as recommended by the 
Committee on Coal Analysis are as follows: 

The Atkinson Method. 1 — "Thoroughly mix on glazed paper 1 grm. of 
the laboratory sample of coal with 7 grm. of dry sodium carbonate 
and spread evenly over the bottom of a shallow platinum or porcelain 

1 /. Am. Chem. Soc, 21, 1128 (1899). 




Fig. 42. — Crucible for 
peroxide fusion. 



208 GAS AND FUEL ANALYSIS 

dish. Place on a triangle slightly elevated above the bottom of a cold 
muffle. Raise the temperature of the muffle gradually until a tem- 
perature of 650° to 700° C. (dull red heat) has been obtained in half 
an hour and maintain this temperature for ten or fifteen minutes. 
The sodium carbonate should not sinter or fuse. The mixture should 
not be stirred during the heating process. When the dish has cooled 
sufficiently to handle, the matter should be examined for black particles 
of unburned carbon and in case such indications of incompleteness of 
the process appear, the dish should be replaced and heated for a short 
time. When all carbon is burned, remove the dish and digest the con- 
tents with 100 to 125 c.c. of warm water. Allow the insoluble matter 
to settle, decant through a filter and wash several times by decantation. 
Transfer to the filter, adding a few drops of a solution of pure sodium 
chloride, if the insoluble matter tends to pass through the filter. The 
washing should be continued until the filtrate shows no alkaline reaction. 
Make the nitrate slightly acid with sufficient concentrated hydrochloric 
acid and precipitate the sulphates with barium chloride as described 
under the Eschka method. No oxidizing agent is required." 

Sulphur may also be determined in the water rinsed from 
the bomb calorimeter after a calorimetric determination, pro- 
vided that the calorimeter is provided with a lining which 
is not attacked by the acid formed. The bomb should be 
very thoroughly rinsed with hot water, the solution filtered 
and precipitated with BaCl 2 as usual. The tendency with 
this method will be toward low results. 

Parr 1 has developed a rapid photometric method for the 
determination of sulphur in coal. The residue from the fusion 
with sodium peroxide is dissolved, acidified, diluted, and pre- 
cipitated cold with a mixture of barium chloride and oxalic 
acid. The precipitated barium sulphate is in a very finely 
divided condition so that it does not settle readily. The 
photometer consists of a graduated tube of special design which 
rests upon a diaphragm below which is a candle flame. The 
emulsion of BaS0 4 and solution is slowly poured into this 
photometer until the sharp outline of the flame disappears. 
The height of solution in the photometer tube gives, by reference 
to a special table, the per cent, of sulphur in the coal. Results 

1 Jour. Am. Chern. Soc, 26, 1139 (1904); Jour. Ind. and Eng. Chem., 1, 
689 (1909). 



THE CHEMICAL ANALYSIS OF COAL 209 

on 35 coals quoted by Parr show good agreement with gravi- 
metric methods. 

11. Ultimate Analysis. — Carbon and Hydrogen. — Carbon and 
hydrogen in coal and coke are determined as is usual in the 
ultimate analysis of organic compounds, by combustion in a 
stream of dry and pure oxygen and absorption of the resulting 
carbon dioxide and water. The analysis is a difficult one 
and should not be attempted by one who has not had practice 
in the general method. If it is necessary for an analyst without 
training in this particular line to undertake such an analysis 
he should practice on the ultimate analysis of such pure com- 
pounds as sugar and benzoic acid until he has attained proficiency. 
Detailed directions for these determinations in coal are given in- 
Technical Paper 8 of the Bureau of Mines. 

In a determination of the heating value of coal in a bomb 
calorimeter, there is complete oxidation of the carbon to carbon 
dioxide and of the hydrogen to water. An absorption train 
may be connected to the bomb and the gases allowed to bubble 
slowly through it. After the pressure in the bomb has fallen 
to that of the atmosphere the bomb may be immersed in a 
dish of hot water and suction applied to the absorption train. 
It is in this way possible to estimate the carbon dioxide and 
water formed in the combustion. Kroeker 1 proposes a bomb 
which has an inlet and an outlet valve so that dry and pure 
air may be passed through the bomb after the pressure has 
been relieved. The method is capable of giving good results 
in skilled hands. Great care must be taken to keep the packing 
on the oxygen valves in perfect condition as otherwise part 
of the products of combustion will escape during the slow 
process of emptying the bomb. There is also a minor error 
due to the oxidation of some of the nitrogen to form nitric acid 
which is reported as carbon dioxide 

Parr 2 has proposed a gas volumetric method of determining 
carbon from the residue of the peroxide fusion in the Parr 
calorimeter. The residue consisting largely of Na 2 C03 and 
Na 2 2 is dissolved in water and treated with acid. Carbon 
dioxide and oxygen are evolved and the carbon dioxide is 

1 Zeit. d. Vereinsf. d. Rubenzuckerindustrie, 46, 177 (1896). 

2 University of Illinois Bulletin Vol. 1, No. 20 (1904). 

14 



210 GAS AND FUEL ANALYSTS 

estimated by absorption. There are a number of minor sources 
of error which make it difficult to get accurate results by this 
method. Sodium peroxide both dry and in solution readily 
absorbs carbon dioxide from the air and care is necessary in 
order to keep the correction factors constant. Difficulty has 
also been experienced in completely boiling off the carbon dioxide 
from the solution. 

12. Nitrogen. — The chief value attaching to a knowledge of 
the per cent, of nitrogen in a coal is the indication which it is be- 
lieved to give of the amount of ammonia which the coal will 
yield on destructive distillation. No attempt is usually made to 
distinguish between the various forms in which nitrogen may exist 
in coal. The total nitrogen is best determined by the Kjehldahl 
method or one of its modifications as regularly used in the 
ultimate analysis of organic compounds. The following de- 
tails are taken from Techinical Paper 8 of the Bureau of Mines. 



"The well-known Kjehldahl method is used in determining nitrogen. 
One gram of the coal sample is boiled with 30 c.c. of concentrated 
sulphuric acid (H 2 S0 4 ) and 0.6 grm. of mercury until all particles of 
coal are oxidized and the solution nearly colorless. The boiling should 
be continued at least two hours after the solution has reached the straw- 
colored stage; then crystals of potassium permanganate (KMn0 4 ) are 
added, a few at a time, until a permanent green color remains. After 
cooling, the solution is diluted to about 200 c.c. with cold water. 
Twenty-five cubic centimeters of potassium sulphide (K 2 S) solution (40 
grm. K 2 S per liter) are added to precipitate the mercury; to prevent 
bumping 1.0 grm. of granular zinc, and, to prevent frothing, a piece of 
paraffine about the size of a brass 1 grm. weight are also added. Enough 
saturated sodium hydroxide (NaOH) solution (usually 80 to 100 c.c.) to 
make the solution distinctly alkaline is next added and the flask is at 
once connected with the condenser. The ammonia (NH) 3 is distilled 
over into a measured amount of standard sulphuric acid solution, to 
which has been added sufficient cochineal indicator for titration. The 
solution is distilled until about 200 c.c. of distillate has passed over, and 
the distillate is titrated with standard ammonia (NH 4 OH) solution (20 
c.c. NH 4 OH solution = 10 c.c. H 2 S0 4 solution = 0.05 grm. nitrogen). 
The transfer to a distillation flask may be avoided by the use of a 500 
c.c. Kjehldahl flask for digestion of the coal, connection being made 
direct from the Kjeldahl digestion flask to the condensing apparatus." 



THE CHEMICAL ANALYSIS OF COAL 211 

13. Phosphorus. — Phosphorus is usually determined only in 
fuels which are to be used for metallurgical processes where the 
fuel is to come in direct contact with the metal. The following 
details are those of the Bureau of Mines. 

"For the determination of phosphorus in coal or coke, a sample 
weighing 6.52 grm. is burned to ash in the muffle furnace. The ash is 
mixed with four to six times its weight of sodium carbonate plus 0.2 
grm. of sodium nitrate, and is fused at the highest temperature of the 
blast lamp. The fused mass is dissolved in water, acidified, and evapo- 
rated to dryness. The residue is taken up in hydrochloric acid, and the 
phosphorus determined in the usual way, either by weighing or by 
titrating the yellow precipitate with permanganate." 

14. Oxygen. — There is no direct method for the estimation of 
oxygen in coal. In an ultimate analysis the percentages of 
carbon, hydrogen, nitrogen, sulphur and ash are added and the 
difference between this sum and 100 per cent, is called oxygen. 
It is thus apparent that any errors in the estimation of the other 
constituents are reflected in the figure for oxygen and that 
therefore this figure is to be regarded as the least significant of 
the analysis. 

15. Methods of Reporting Analyses. — The analysis is usually 
made on the air-dried sample since the sample in this form is 
least liable to change. The original figures obtained by the 
analyst will therefore be for coal in this form. He may now 
take into account the moisture lost in air-drying and calculate 
the analysis to a basis of coal "as received," he may mathemat- 
ically eliminate all the water and report as "Coal free from Mois- 
ture/' or he may by calculation eliminate both the moisture and 
ash and report as "Coal free from Moisture and Ash." 

Numerous attempts have been made to calculate "true coal" 
or "coal substance" by elimination, in addition to the moisture 
and ash, of water of hydration contained in shale, and carbon 
dioxide contained in carbonates of the ash — both of which are 
driven off in whole or in part with the volatile matter whereas 
they really belong to the ash. Such corrections are difficult to 
apply and are not often made in technical work. If any event the 
data reported should be sufficient to allow a recalculation of the 
results to any other basis. Ordinarily the air-drying loss and 
analysis of air-dried coal are reported since they are the figures 



212 



GAS AND FUEL ANALYSIS 



actually obtained by the analyst and in addition whatever other 
forms of report may be called for. The following analysis of a 
Pittsburg coal shows the form of report. 

PERCENTAGE COMPOSITION OF COAL 



Proximate analysis 


Air-dried 


As received 


Calculated 
moisture- 
free 


Calculated 

moisture and 

ash-free 


Moisture 


1.07 
34.55 
58.51 

5.87 


3.94 
33.55 
56.81 

5.70 






Volatile matter 

Fixed carbon 


34.93 

59.14 

5.93 


37.13 

62 87 


Ash 






100.00 


100.00 


100.00 


100.00 



Ultimate analysis 

Hydrogen 

Carbon 

Nitrogen 

Oxvgen 


5.16 
79.52 
1.41 
6.97 
1.07 
5.87 


5.33 
77.21 
1.37 
9.35 
1.07 
5.70 


5.09 

80.38 
1.43 
6.09 
1.08 
5.93 


5.41 

85.44 

1.52 

6.48 


Sulphur 

Ash 


1.15 




100.00 


100.00 


100.00 


100.00 


Air-drying loss 




. 
















16. Accuracy of Results. — It will be evident from a consider- 
ation of this chapter and the preceding one on sampling that the 
error in sampling is liable to be larger than the error of analysis. 
The Joint Committee on Coal Analysis in its 1913 report esti- 
mates the allowable variations under its new methods of analysis 
as follows: 



Different 
analysts, 
per cent. 



Moisture, under 5 per cent 

Moisture, over 5 per cent 

Volatile matter, bituminous coals. 

Volatile matter, lignites 

Ash, no carbonates present 

Ash, carbonates present 

Ash, more than 12 per cent 

Sulphur, in coal 

Sulphur, in coke 




0.3 
0.5 
1.0 

2.0 

0.3 

0.5 

1.0 

0.1 . 

0.05 



THE CHEMICAL ANALYSIS OF COAL 213 

The greatest variation is in the volatile matter and when a con- 
tract is to be awarded in which an accurate determination of 
volatile matter is demanded, it is advisable for the purchaser and 
the bidder to jointly analyze a single sample of coal and harmon- 
ize their differences in analytical procedure before the contract 
is awarded. Lord, 1 from his wide experience, states that in 
ultimate analysis the accuracy can be safely stated as within 
0.05 per cent, in the case of hydrogen, perhaps 0.3 per cent, on 
carbon, 0.03 per cent, on nitrogen and 0.05 per cent, on sulphur. 
17. Slate and Pyrites. — It is frequently desirable to determine 
how much of the pyrites and slate is in a form which will permit 
mechanical separation by coal-washing or otherwise. Lord 2 
recommends the use of calcium chloride solutions with which a 
specific gravity as high as 1.35 may be obtained or zinc chloride 
solutions with which a specific gravity of 2.0 may be reached. 
The coal is tested by crushing to various degrees of fineness and 
determining the differences in composition of the portion which 
floats and that which sinks in solutions of varying specific 
gravities. 

1 Jour. Ind. and Eng. Chem., 1, 307 (1909). 

2 Jour. Ind. and Eng. Chem., 1, 308 (1909). 



CHAPTER XVI 
HEATING VALUE OF COAL BY THE BOMB CALORIMETER 

1. General Methods of Determining Heating Value. — The 

heating value of a fuel is determined either directly in a calori- 
meter or indirectly by calculation from its chemical composition. 
The direct calorimetric method involves the combustion of the 
fuel by oxygen supplied either as free oxygen gas or as combined 
oxygen of some chemical compound, the operation being carried 
out in a closed vessel immersed in a known mass of water under 
conditions which ensure that the heat evolved in the oxidation 
shall be with as little loss as possible transferred to and retained 
by the calorimetric vessel and the water. The heat evolved is 
calculated from the rise in temperature of the system. 

Modern methods of calorimetry really commenced with the 
invention by Berthelot of his bomb calorimeter described in 1881. 1 
This has become the standard method for the determination of 
heating values and therefore the whole of this chapter is devoted 
to it. Other methods, especially that of Parr, are described in 
the following chapter. 

2. The Bomb Calorimeter. — Berthelot showed that if combus- 
tion of carbon compounds took place in a closed vessel in an atmos- 
phere of oxygen compressed to at leat seven atmospheres and with 
a weight of combustible such that only 30 to 40 per cent, of the 
oxygen initially present was consumed, combustion was rapid and 
complete. His bomb was lined with heavy platinum and was 
very expensive. Hempel in the second edition of his gas anal- 
ysis published in 1889 described a much cheaper bomb which had 
no lining at all. His modification has been found by the author 
to be mechanically unsatisfactory. The neck of the bomb is 
constricted so that it is difficult to dry the interior, and the head- 
piece is threaded and screws into the neck roughening the lead 

1 Annates de Chimie, 5 Serie, 23, 160 (1881). Annales de Chimie, 6 Serie, 
6, 546 (1885). 

214 



HEATING VALUE OF COAL BY THE BOMB CALORIMETER 215 

gasket as it turns upon it. The method of making connection 
to the oxygen tank is also unsatisfactory. 

Mahler 1 in 1892 reported a careful study of Berthelot's method 
as applied to coals, and described a bomb of improved construc- 
tion with an enamel instead of a platinum lining. This bomb is 
mechanically better than Hempel's, but there is still the objec- 
tion that the top as it screws down, roughens the gasket. 

Atwater 2 in 1894 described a modification of the bomb calori- 
meter distinctly superior mechanically to the preceding forms. 
It resembled more closely the Berthelot bomb than either of the 
others but, whereas the Berthelot bomb was closed by a tapered 
plug held in place by a screwed cap, Atwater's was closed by a 
flat cap held in place by a collar slipped over it and screwed over 
threads on the outside of the bomb after the manner of a union 
pipe-fitting. In this way all tearing of the gasket was avoided. 
The Atwater bomb may be provided with a gold or platinum 
lining and is to be regarded as the highest type of instrument 
for research work. 

Many modifications of the bomb calorimeter have been made 
by other workers, but the principle has not been changed. Any- 
one familiar with one instrument can readily learn to use any 
other. 

3. Details of the Bomb Calorimeter. — The bomb calori- 
meter which has been in use in the calorimeter laboratory of the 
University of Michigan since 1908 is shown in Figs. 43 and 44. 
It is in general patterned after the Atwater bomb, but possesses 
several improvements. One of these, due to Mr. Edwin H. 
Cheney, is the octagonal belt on the body of the bomb which fits 
into a recessed plate and holds the bomb rigidly while the cover is 
being screwed on. Another, due to Professor S. W. Parr, is the 
deeply recessed groove for the gasket in the cover of the bomb 
into which the straight lip of the bomb fits closely so that a 
rubber gasket may safely be used. Improvements in various 
details are due to Mr. J. H. Stevenson, instrument maker of the 
University of Michigan. Details of the bomb are shown in 
Fig. 43. It consists of a cylinder of about 300 c.c. capacity 

1 Bui. de la Societe d. Encouragement, 1892, 319. 

2 Starrs Conn. Experiment Station Report, 1894, 135; also J. Am. Chem. 
Soc., 25, 659 (1903). 



216 



GAS AND FUEL ANALYSIS 



machined from a solid block of steel. On this sits a cover carry- 
ing the oxygen inlet and needle valve, also machined from a 
solid piece of steel. The cover is pressed tightly into place on 
the bomb by a heavy ring cap screwing over it and drawn up 
tightly by a spanner. Compressed oxygen is admitted through 
a flexible metal tube soldered at A to the steel tube with the coned 
head B. This tube AB slides freely in the threaded sleeve C. 
Its coned head makes a gas tight joint with the bomb when C 



o 
1 






H 


o o 



''//w?7///////?777m////, 



'////W//////////////////)//////////////> 




Fig. 43. — Details of calorimetric bomb. 



is screwed up. The needle valve D closes the bomb when it is 
screwed down. The coal sits in a flat nickel capsule E supported 
on a brass ring which screws into the head piece. The insulated 
electrical connection FG is a brass rod coned where it passes 
through the head piece from which it is insulated by a bit of thin 
rubber tubing. The binding post G screwing down on the 
threaded end of F which projects through the cover pulls the 
cone tightly into its seat and makes a gas tight joint. A mica 
disc placed between the binding post and the bomb completes 



HEATING VALUE OF COAL BY THE BOMB CALORIMETER 217 

the electrical insulation of the electrode from the bomb. The 
gasket which fits into the groove H may be of lead, hard 
fiber or rubber. Rubber gives a tight joint with the least pres- 
sure of the spanner and is therefore to be preferred. If it is cut 
to fit the groove accurately the inner lip of the bomb projecting 
into the recessed head will effectually protect it from the hot gases 
evolved in the bomb during combustion. 

Fig. 44 shows the various parts of the calorimeter. Two bombs 
are shown, one assembled and one taken apart and with the head 
sitting on a stand in position for adjustment of the fine iron 




Fig. 44. — Bomb calorimeter. 



firing wires. The nickel-plated copper can, the stirrer and the 
insulating buckets are also shown. 

The insulating buckets as shown in Fig. 44 consist of two con- 
centric fiber pails with air in the space between them. It is in 
many ways preferable to have this space filled with water, whose 
temperature may be set at any desired point. This minimizes 
the effect of draughts in the room and enables the operator to use 
a Beckman thermometer without having to shift its zero when 
the room temperature fluctuates. The temperature of the water 
must not, however, be so far below room temperature that dew 
will deposit on the walls of the calorimeter vessel. When a water 
jacket is thus used in the calorimeter, it should be provided with 
a stirrer and its temperature should be recorded. 



218 GAS AND FUEL ANALYSIS 

4. Thermometers. — Thermometers for the calorimeters should 
be made especially for the purpose with a stem below the gradua- 
tions long enough to allow the bulb of the thermometer to be 
opposite the center of the bomb. The entire length of the grad- 
uated portion of the thermometer should be visible above the 
calorimeter lid. It is necessary that it be possible to read the 
rise in temperature to at least 0.01° C. The best thermometers 
are those of the Beckman type with a scale length of 6° and a 
zero point adjustable between 12° and 25°. This type of ther- 
mometer is always to be recommended where the calorimeter 
room is of relatively constant temperature so that it is not 
necessary to change the zero point often. Where this desirable 
condition is not fulfilled calorimetric thermometers with a fixed 
scale running from 15° to 30° C. must be used. These are usually 
divided only into 0.02° to avoid the excessive length of stem 
which would otherwise result. The thermometer should in any 
case have been carefully calibrated since an error of 0.01° on the 
average rise of 3° means 0.3 per cent, or approximately 40 B.t.u. 
per pound of coal. 

5. Preparation of Sample. — The methods to be followed in ob- 
taining a representative sample from a large quantity of coal and 
the precautions necessary in grinding, sampling and drying this 
large sample have been given in Chapters XIV and XV. It is 
assumed here that the sample is already ground to a fineness of at 
least 60-mesh and has been air-dried. The amount of moisture 
is immaterial so far as the operation of the bomb calorimeter is 
concerned, but an air-dried sample is less likely to change during 
the operation of weighing. 

When powdered bituminous coal is burned in compressed 
oxygen, combustion is so violent that there is danger that gas and 
even solid particles will be projected unburned through the flame 
zone. The rate of combustion may be materially lessened by re- 
ducing the surface of coal exposed to the oxygen. This is best 
accomplished by briquetting the coal. Most bituminous coals 
may be readily compressed into pellets in a screw press. The 
pressure should be slowly applied and allowed to remain for a few 
minutes. The resulting pellet may be trimmed to approximate 
weight with a penknife. It is advantageous to break it into 
two or more pieces and discard the dust before weighing. The 



HEATING VALUE OF COAL BY THE BOMB CALORIMETER 219 

advantage of cutting the pellet lies in the readier ignition, for 
pellets which have been pressed very hard are sometimes so dense 
on the surface that they fail to ignite. It is possible to com- 
press some bituminous coals so firmly on the surface that the 
gas evolved in the interior of the briquette by destructive dis- 
tillation explodes the briquette and blows a cap of coke out of 
the crucible. If these dense briquettes are cut into several 
pieces, as directed above, the trouble will be obviated. It is not 
necessary to briquet anthracite coals or coke. Indeed, it is not 
possible to do so without the addition of a binder such as sugar 
or bituminous coal. 

6. Manipulation of Bomb Calorimeter. — The bomb is taken 
apart and examined to see that it is in good condition and that 
the gasket is not cut. A few drops of water are placed in the 
bottom part of the bomb which is set in its receptacle in the 
table-top. The top part of the bomb is placed on a ring of an ordin- 
ary ring stand as shown in Fig. 44 which allows the heavy termin- 
als to drop through in a convenient position for adjustment of the 
fuse wire and sample. The weighed sample of coal is placed on a 
shallow thin nickel or platinum capsule resting on the supporting 
ring suspended from the head of the bomb. The capsule must be 
almost flat to allow free access of oxygen from the edges as the 
flame flares up. Otherwise combustion may be incomplete. It 
must be thin or it will chill the flame and prevent complete com- 
bustion. It is advisable with anthracite and coke to place a thin 
pad of ignited asbestos on the capsule in order to decrease still 
further the cooling effect of the metal. 

A measured length, preferably not more than two inches, of 
the fine iron ignition wire 34 B. & S. gage is attached to the 
heavy wire terminals by winding the ends of the fine wire several 
times around the heavy ones, leaving the fine wire in the form 
of a loop between the terminals. After making connections the 
loop is pushed down until it rests on the fragments of coal. 
Care is to be taken that the wire does not touch the metal capsule 
and form a short circuit. 

The cover with the sample in position is placed carefully 
on the bomb and the threaded collar slipped over it and screwed 
down, pressure finally being applied with the spanner. A 
novice will nearly always screw the cover down harder than 



220 GAS AND FUEL ANALYSIS 

necessary, thus shortening the life of the gasket. A moderate 
pressure will suffice if the gasket is a good one. Gaskets cut 
from ordinary red fiber packing are too porous to be tight 
unless screwed down with great pressure. They may be much 
improved by vacuum impregnation with a solution of 5 grm. of 
glue in 5 c.c. of glycerine and 100 c.c. of water. After impregna- 
tion the gaskets are to be dried in air and rubbed with a piece 
of paraffine to keep them from sticking to the metal. 

The loose joint on the end of the flexible metal tube from the 
oxygen tank is screwed into the head of the bomb, the needle 
valve of the bomb opened at least a full turn, and then the 
valve on the oxygen tank is opened slightly, the gas entering in a 
slow stream from the tank until the gage shows 20 atmospheres 
pressure. If the valve on the tank is opened relatively more 
than the one on the bomb the gage between the two may show 
20 atmospheres before there is that much pressure in the bomb. 
The oxygen valve on the tank is to be closed first and after that 
the valve on the bomb. If the valve on the bomb is closed 
before that on the tank, the pressure on the gage will rise very 
quickly to the full pressure of the oxygen tank which may be 
2000 lb. and the gage may be blown up. 

The bomb is disconnected and placed in the water of the 
calorimeter or in a separate vessel of water to test for leaks. 
If bubbles of gas appear around the threaded ring the cover 
must be screwed down more tightly, and possibly the gasket 
may have to be replaced. If bubbles of air come from the 
head it is evident that the needle valve is leaking. It is worse 
than useless to try and force it to become tight by screwing down 
the needle with great pressure. A needle valve truly ground 
into its seat is tight with slight pressure. If a particle of grit 
comes between the metal surfaces the application of pressure 
causes it to scour the polished surface and the valve will leak 
until it has been again ground to a true surface. In case of a 
leaking needle valve the pressure must be relieved, the bomb 
opened and the needle valve unscrewed entirely out of the 
head. The lock nut into which it was threaded is also to be 
removed. The coned seat into which the needle valve is ground 
may now be seen in a strong light. The best policy is to grind 
the needle valve into its seat, an operation requiring not more 



HEATING VALUE OF COAL BY THE BOMB CALORIMETER 221 

than ten minutes if the valve has not been abused. The needle 
valve is dipped into a paste of fine emery or carborundum 
in water and ground into its seat by rotating it back and forth 
with the fingers. A polished ring will soon be visible on the 
cone point and a corresponding ring in the seat. When this 
appears, unless the metal has been badly scratched, the process 
may be considered complete and the grinding interrupted. 
The valve is to be thoroughly cleaned from grit and dried, when 
it is ready for use. 

The bomb when charged is to be carefully centered in the 
calorimeter vessel which is in turn centered in the outer vessels. 
The stirrer and thermometer are placed in position and two 
liters of water whose temperature is approximately 3° below 
room temperature is added. A glass flask which holds 1000 
c.c. of water, contains the following weights of water, when 
balanced against brass weights in air. 1 

15° C 998.05grm. 

20° C 997.18grm. 

25° C 996.04grm. 

30° C 994.66grm. 

The liter flasks of various makers differ in the amount of 
water which they discharge and the flask should be calibrated 
by direct weight for some one temperature. It is more con- 
venient for calculation purposes to calibrate the flask to deliver 
2000 grm. of water at the temperature most frequently used, 
or sometimes to deliver such an amount of water that the sum 
of the water added and the water value of the calorimeter shall 
be 2500 grm. It is in many ways better to weigh the water di- 
rectly into the counterpoised calorimeter vessel as it sits on the 
balance. 

Especial care is to be taken to see that the thermometer is 
centered in the space between the bomb and the edge of the 
vessel. If it touches either, or even if it is a little off center 
the rise of the thermometer will not be even and the result 
may be in error. 

After. the adjustments are complete the stirrer is operated 
for at least two minutes before the first temperature reading 

1 Bureau of Standards Bull. 4, 600 (1907-08). 



222 GAS AND FUEL ANALYSIS 

is made on an even minute. Readings are to be made each 
minute thereafter for at least five minutes, the stirrer being 
kept going steadily at 30-40 strokes per minute and the tempera- 
ture slowly and steadily rising with each reading as heat is 
absorbed from the air of the room, or dropping if the calorimeter 
is above room temperature. This ends the preliminary period, 
which must show at least five readings changing by regular 
increments due solely to heat transfer to or from the outside air. 

The firing circuit is closed simultaneously with the last 
reading of the preliminary period. The iron wire becomes 
heated to redness, the coal ignites and the iron wire fuses almost 
instantly. It is well to have an electric lamp in the firing circuit 
which lights when the current is turned on and is extinguished 
when the wire fuses. An ammeter in the circuit answers the 
same purpose showing that the ignition is prompt and that an 
undue amount of heat is not imparted to the calorimeter by the 
electric current. Current for ignition may best come from a 
storage battery or group of dry cells giving about 12 volts. 
Higher voltages are apt to cause insulation troubles. 

Within a half minute after ignition the thermometer begins 
to rise so rapidly that it is not possible to make the thermometer 
readings accurately. They should be taken as accurately 
as possible, and regularly on each minute. After about three 
minutes the thermometer reaches its maximum, but the stirring 
and temperature readings must be kept up without intermission 
for a total of ten minutes after ignition to obtain data for the 
radiation corrections. 

' After the termination of the thermometer readings the bomb is 
removed from the calorimeter, wiped dry, and placed in its recep- 
tacle on the table. The needle valve is opened and after the 
pressure is relieved the top is removed. The coal should be 
perfectly burned and the ash should appear as fused beads. The 
iron wire has burned as far as the heavy conductors and in 
accurate work the length of the wire unburned should be deter- 
mined to enable the proper correction to be made for the weight of 
wire burned. The weight of wire burned comes to be almost 
a constant for each operator and may be taken as such in ordinary 
work. If soot appears in the bomb or on the capsule, the deter- 
mination should at once be rejected. With inexperienced ope- 



HEATING VALUE OF COAL BY THE BOMB CALORIMETER 223 

rators this trouble is frequently caused by opening the valve on the 
oxygen tank too fast when filling the bomb, with the result that 
the gage on the connecting tube jumps to the proper reading 
before the indicated pressure is reached in the bomb. If trouble 
persists it may be necessary to increase the oxygen pressure to 
25 atmospheres. The bomb is to be rinsed out carefully and 
unless it is to be used again at once, is to be dried best in an oven 
at a temperature of about 35-40° C. If the bomb is not dried in 
this way rust is almost certain to form in the needle valve and 
prevent it from closing tightly. 

7. Thermometer Corrections. — The calorimetric thermometer 
should have the certificate of the Bureau of Standards. In addi- 
tion to the corrections indicated on the certificate as inherent 
in the thermometer on account of variation in the diameter of the 
capillary tube, etc., minor corrections must be made in accurate 
work for variations due to the conditions under which the ther- 
mometer is used. The Bureau of Standards calibrates ther- 
mometers when totally immersed in a bath of the temperature 
indicated. In calorimetric work the bulb and part of the stem is 
within the calorimeter, while part of the stem proj ects through the 
cover of the calorimeter into the air of the room. A small 
correction must be made for this emergent stem. In the case 
of Beckmann thermometers an additional "setting factor correc- 
tion" must be used in case the thermometer is set for a different 
zero from that used in the calibration. The formulae for these 
corrections vary with different sorts of glass and are given in 
full in the certificate of calibration accompanying each ther- 
mometer. The corrections rarely amount to more than a few 
thousandths of a degree. 

8. Radiation Corrections. — The combustion of the coal in a 
bomb calorimeter is probably a matter of only a few seconds, but 
it requires several minutes for the heat to be transmitted to the 
water and for the thermometer to register the rise in temperature. 
Adiabatic calorimeters have been constructed, 1 but they are not 
technical instruments. With the usual type of instrument radia- 
tion corrections must be made in spite of careful jacketing of the 
calorimeter. Their magnitude is lessened by adjusting the tem- 
perature of the water placed in the calorimeter with reference to 

1 Richards and Jesse, J. Am. Chem. Soc, 32, 268 (1910). 



224 GAS AND FUEL ANALYSIS 

room temperature and to the rise in temperature expected. If 
the rise in temperature is to be 3°, the water poured into the calori- 
meter should be about 3° below room temperature. When 
equilibrium is reached at the time of ignition the temperature 
will be about 2.5° below that of the room and after combustion 
it will be about 0.5° above room temperature. This arrange- 
ment minimizes the errors. The temperature rises very rapidly 
after ignition to one so nearly that of the room that changes due 
to radiation are slight and repeated readings may be made to 
obtain the final temperature. If the final temperature of the 
calorimeter is slightly above that of the room there should be a 
maximum point in the thermometer readings with a slow decrease 
thereafter. 

It is common practice to consider that the maximum ther- 
mometer readings represent the actual maximum temperature of 
the calorimeter, but it is not a safe assumption, for if the ther- 
mometer bulb is unduly close to the bomb or if the stirring is 
inefficient the thermometer may rise too high and fall rapidly 
again to the temperature representing the true average value of 
the system, after which it will change slowly and regularly through 
radiation. It is, therefore, unsafe to use the maximum temper- 
ature in calculations. The final temperature of the combustion 
period should be taken only after sufficient time has elapsed so 
that it is certain that the system has come to equilibrium. Five 
minutes is usually sufficient. 

Radiation corrections are based on the principle that the inter- 
change of heat between the room and the calorimeter is propor- 
tional to the difference in the temperature between them. The 
temperature of the room is assumed to be a constant during any 
one operation and need- not even be known. The formula for the 
correction as used by Regnault and developed by Pfaundler 1 is 
somewhat complicated in appearance, but is simple in use. 

Regnault-Pfaundler Formula. — Three sets of temperature read- 
ings are to be made. The initial set must not start until after the 
temperature of the calorimeter has commenced to change 
regularly due to radiation. It consists of at least five readings 
made one minute apart. Only the first and last readings and 
the time interval enter into the calculation, but it is advisable to 

1 Poggendorfs AnnaUn, 129, 115 (1866). 



HEATING VALUE OF COAL BY THE BOMB CALORIMETER 225 

record the intermediate readings as a check on the accuracy of the 
two important ones and to make sure that the change of temper- 
ature is uniform as it should be. At the moment of taking the 
final reading of the initial period the firing key is pressed and the 
reading just taken is recorded, both as the final reading of the 
initial period and the first reading to the combustion period. It 
is to be marked T . 

During the combustion period readings are to be made and 
recorded regularly not only till the thermometer reaches its 
maximum, but also till it is certain that the changes in tempera- 
ture are again due solely to radiation. This period may be five 




A a, a z a r A' 

Fig. 45. — Diagram showing derivation of Regnault-Pfaundler formula. 

to ten minutes. There follows a final period of five minutes to 
fix the radiation losses for the latter portion of the test. 

The derivation of the Regnault-Pfaundler formula is as follows : 



To, 

ti, t ; 



Let t = mean temp, of initial period. 
t' = mean temp, of final period. 
v=loss per time interval in initial period, 
v' — loss per time interval in final period. 
Ti, T 2 , T n = temperature readings in combustion period. 
, . . . . t n = average temp, of each interval during combus- 



tion period; 



• + To + T i + 
i.e., ti = — ~ — , etc. 



The special case assumed by Pfaundler is one where the initial 
temperature is only slightly different from room temperature, 
giving a small value for v. The final temperature is considerably 
above room temperature and the value of v' is larger than v. The 
geometrical construction for the Regnault-Pfaundler formula is 
shown in Fig. 45. The demonstration is as follows: 

15 



226 GAS AND FUEL ANALYSIS 

Lay off OA = t. 

Lay off OA' = t'. 

Lay off Oai = ti. Oa 2 = t 2 .... Oa n = t n 
At A erect perpendicular AV = v. 
At A' erect perpendicular A / V / = v / . 

Join V and V by a straight line and at ai a 2 . . . . a n erect 
perpendicular intersecting VV. 
Any ordinate a r V r = AV+ p V r . 

A'V'-AV 

On account of similar triangles p V r = j-j- f — pV. 

A'V'-AV 
a T V r = AV+ AA / P V. 

v r — V 

=v +t^t (tr " t) - 

C = the algebraic sum of all the ordinates = correction sought. 

n = the number of observations in the combustion period 

proper. 

v' — v 
C = nv+Y~ jr(ti+t 2 .... t n -nt). 

= nv+Y^(T 1 +T 2 +T 3 .... T n _ 1 +"°y—-nt). 

Heat received by the calorimeter from the outside air is con- 
sidered as negative and therefore in the especial case assumed by 
Pfaundler where the initial temperature was slightly under room 
temperature v was negative. 

The correctness of the formula is independent of the relative 
values and signs of v and v'. 

The corrected rise in temperature of the calorimeter 

R = T n -TofC 

The need of an elaborate correction for radiation is naturally 
less when the calorimeter is provided with an adequate stirrer 
so that the heat interchange between the bomb and the water is 
quickly effected, and also less when the insulating jacket is good 
than when it is poor. With a well designed calorimeter the 
largest part of the rise in temperature occurs in the first minute 
and if the final temperature is only slightly above room tempera- 
ture radiation in succeeding minutes is almost negligible. 



HEATING VALUE OF COAL BY THE BOMB CALORIMETER 227 

SAMPLE OF RECORD 

Determination of Heating Value of Coal in Bomb Calorimeter. 
Sample No. U. 38 Date Nov. 10, 
Calorimeter No. 2 Thermometer No. 4 
Water Value of Calorimeter . 475 grm. 
Water Used 2000 c.c. = 1995 grm. 

Total water equivalent 2470 grm 



Sample of coal (air 


-dried) 0.9922 grm. 


Thermometer readings 




by minutes 




Factors 


19.68 






v =-0.0025 


19.68 






v' =+0.0025 


19.69 






t =19.69 


19.69 






t' = 23.11 


19.69 


To 






21.4 


Tx 




T!+T 2 +T 3 + T 4 


22.58 


T 2 




T + T 5 „„ s 


22.95 


T 3 




2 =21,4 



90.0 



23.09 T 4 
23.11 T 5 

n=5 
23.11 
23.11 Thermometer corrections 

23.10 T n =23.11-0.045=23.065 
23.10 To =19.69-0.040 = 19.65 

5X-0. 0025 + Q 23 Q0 i 2 i 5 -^i'q Q0 6 ^ (90.0+21.4-5X19.7) = +0.006° C. 
R =23.065-19.65+0.006=3.421° C. 
3 . 42 1 X 2470 = ,8450 calories 



Deduct for 0.025 grm. fuse wire 40 

Deduct for 1.0 per cent, sulphur 

(20 X . 9922) = 20 60 



8390 calories 



8390 „ Arr . . ,.,.-,-,' 

anno = 8455 calories per gram of air-dried coal 

8455X1.8 = 15,219 B.t.u. per pound of coal. 

Proximate Analysis of Coal 

Moisture 0.32 per cent. 

Volatile Matter 22.87 \ nr - 

tt j ^ T. ^ o« > 95 . 5 per cent. 

Fixed Carbon 72.67 J 

Ash 4.14% 



100.00 
Heat evolved per pound coal dry and free from ash = — q^ = 15936 B.t.u. 



228 GAS AND FUEL ANALYSIS 

The Dickinson Formula. — H. C. Dickinson of the Bureau of 
Standards proposes a simpler formula whose derivation has not 
yet been published. The method of using this formula as pub- 
lished in the preliminary report of the Committee on Coal 
Analysis is given below. 

" Observe (1) the rate of rise (ri) of the calorimeter temperature in 
degrees per minute for four or five minutes before firing, (2) the time 
(a) at which the last temperature reading is made immediately before 
firing, (3) the time (b) when the rise of temperature has reached six- 
tenths of its total amount (this point can generally be determined by 
adding to the temperature observed before firing sixty per cent, of the 
expected temperature rise, and noting the time when this point is 
reached), observe (4) the time (c) of a thermometer reading taken when 
the temperature change has become uniform some five minutes after 
firing, (5) the final rate of cooling (r 2 ) in degrees per minute for five 
minutes. 

" The rate ri is to be multiplied by the time b — a in minutes and tenths 
of a minute, and this product added (subtracted if the temperature were 
falling at the time a) to the thermometer reading taken at time a. The 
rate r 2 is to be multiplied by the time c — b and this product added 
(subtracted if the temperature were rising at the time c and later) 
to the thermometer readings taken at the time c. The difference 
of the two thermometer readings thus corrected, provided the cor- 
rections from the certificate have already been applied, gives the 
total rise of temperature due to the combustion. This multiplied 
by the water equivalent of the calorimeter gives the total amount of 
heat liberated. This result, corrected for the heats of formation of 
nitric and sulphuric acids observed and for the heat of combustion of 
the firing wire when that is included, is to be divided by the weight of 
the charge to find the heat of combustion in calories per gram. Calories 
per gram multiplied by 1.8 give the B.t.u. per pound. 
Example : 

Observations 

Water equivalent 2550 grm. 
Weight of charge 1.0535 
Approximate rise of temp. 3.2° 
60 per cent, of approximate rise 1.9° 



HEATING VALUE OF COAL BY THE BOMB CALORIMETER 229 

Corrected temp. 
(Thermometer corrections from the certificate.) 



15.276° 
Charge fired 

18.497 c 



Time 


Temp. 


10-21 


15.244° 


22 


15.250 


23 


15.255 


24 


15.261 


25 


15.266 


(a) 26 


15.272 


(b) 27- 


12 17.2° l 


(c)31 


18.500° 


32 


18.498 


33 


18.497 


34 


18.496 


35 


18.494 


36 


18.493 



Computation 

r ! = 0.028° -T- 5 = 0.0056° per minute, b - a = 1 .2 minutes 

The corrected initial temperature 

is 15.276°+0.0056°X 1.2 = 15.283°. 

r 2 = 0.007° + 5 = 0.0014° per minute; c-b = 3.8 minutes 

The corrected final temperature is 18.497°+0.0014X 

3.8 = 18 . 502° 

Total rise 18.502° -15.283° . . = 3.219° 

Total calories 2550X3.219 = 8209 

Titration, etc — 7 

Calories from 1.0535 grm. coal 8202 

Calories per gram 7785 

or B.t.u. per lb 14013 

In practice, the time b — a will be found so nearly constant for a 
given calorimeter with the usual amounts of fuel that b need be de- 
termined only occasionally. 

9. Corrections for Oxidation of Nitrogen. — When coal is 
burned on a grate minute amounts of oxides of nitrogen are 
formed by the combination of some of the nitrogen of the air and 
possibly also of the fuel with the oxygen of the air. At the higher 
temperature of combustion in the compressed oxygen of the cal- 
orimeter more oxides of nitrogen are formed and account should 

1 The initial temperature is 15.27°; 60 per cent, of the expected rise is 1.9°. 
The reading to observe is then 17.2°. 



230 GAS AND FUEL ANALYSIS 

be taken of the heat evolved in their formation. The heat of 
formation of aqeous nitric acid from nitrogen, oxygen, and water 
is represented, according to Thomsen, by the following equation. 

2N+5O + H 2 O = 2HNO 3 +29800 calories. 

This corresponds to 1058 calories per gram of nitrogen or 238 
calories per gram of HN0 3 . The nitric acid formed may be esti- 
mated in bombs with platinum or gold linings by rinsing out the 
bomb and titrating the washings with standard alkali. From 
this total acidity is deducted the sulphuric acid formed and the 
balance is considered nitric acid. The amount of nitrogen oxi- 
dized is roughly about one per cent, of the total nitrogen present 
whether introduced as free nitrogen with the oxygen or as com- 
bined nitrogen of the coal. The correction is not" usually more 
than 8 calories and may be considered to be offset by the heat 
absorbed in keeping the gases in the calorimeter at constant 
volume. (See § 12.) 

10. Corrections due to Oxidation of Sulphur. — When sulphur 
or pyrites burns in the air only about 5 per cent, of the sulphur 
is oxidized to SO3, the rest of it remaining as SO2. When com- 
bustion takes place under high oxygen pressure in the bomb calor- 
imeter a much larger percentage burns to SO3 and correction 
must be made for it. The equations are: 

S+20 = S0 2 gas +69,100 calories 

S+30 + H 2 (excess) = dilute H 2 SO 4 +141,100 calories. 

One gram of sulphur burning to S0 2 evolves 2165 calories and 
to dilute H 2 S04 evolves 4410 calories. There should therefore 
be a deduction made of 2245 calories for each gram of sulphur thus 
oxidized in the bomb. The determination of this oxidized sulphur 
requires a chemical analysis of the washings from the bomb which 
adds greatly to the amount of work required. The difficulty is 
enhanced by the fact that sulphur may be present in coal as free sul- 
phur, as sulphur in organic combination, as pyrites or as calcium 
sulphate and that the corrections will vary for each of these various 
forms. For free sulphur burning to H 2 S04 the correction will be 
2245 calories per gram as given above, for sulphur as pyrites 2042 x 
calories, while for sulphur as gypsum or sulphate of iron no cor- 

1 Somermeier J. Am. Chem. Soc, 26, 566 (1904). 



HEATING VALUE OF COAL BY THE BOMB CALORIMETER 231 

rection is to be made since it is already in the oxidized form. The 
situation is further complicated by the fact that free sulphur and 
sulphur in organic combination do not burn completely to SO 3 in 
the bomb calorimeter although apparently the sulphur of pyrites 
does burn completely. It is customary to assume that all of the 
sulphur in coal exists in the form of pyrites and to deduct two 
calories for each milligram of sulphur in the sample of coal. This 
procedure is not above criticism for Parr 1 has shown that the 
amount of sulphate in fresh coal may be as high as one per cent, 
and that it doubles after six months storage of the ground sam- 
ple in the laboratory. 

A source of error which should be considered here is that due to 
the possible action of the dilute sulphuric acid formed upon the 
inner surface of an unlined bomb. The bomb soon becomes coated 
with oxide on its inner surface so the action will be between iron 
oxide and sulphuric acid. According to Thomsen the reaction 
Fe 2 03XH 2 0+3H 2 S04 (dilute) evolves 33,840 calories. This 
means 353 calories for each gram of sulphur involved or 3.5 
calories as the maximum error involved for 1 grm. sample of a 
coal containing 1 per cent, of sulphur. The error from this source 
is totally negligible. An expensive calorimeter lined with gold or 
platinum is unnecessary except where the greatest refinements of 
accuracy are sought. 

11. Correction Due to Combustion of Iron Wire. — The iron 
fuse wire which burns to Fe3C>4 evolves 1600 calories per gram, or 
1.6 calories per mg. of iron burned. 

12. Reduction to Constant Pressure. — Combustion in the 
bomb calorimeter takes place at constant volume whereas in 
ordinary furnace work combustion takes place at constant 
pressure. Wherever a decrease in volume takes place on combus- 
tion as where oxygen unites with hydrogen to form water which 
condenses, the gases in the calorimeter which should normally 
have contracted after combustion have had work done upon them 
to keep them at constant volume with the disappearance of an 
equivalent amount of heat. The correction amounts to 541 cal- 
ories for each gram molecule of gas which disappears. 

When gaseous oxygen combines with carbon to form CO2 there 
is no change of volume and hence no correction. The oxygen in 
1 Jour. Ind. and Eng. Chem. 5, 523. (1913) 



232 GAS AND FUEL ANALYSIS 

the organic matter of the coal, may for the purposes of this cal- 
culation be considered to unite with the hydrogen of the coal to 
form water. No correction is needed here since both the hydrogen 
and the oxygen were in the solid state before combustion and the 
water formed is a liquid. 

There is always present in coal an excess of hydrogen over that 
sufficient to combine with the oxygen and this so-called available 
hydrogen burns with gaseous oxygen to form water which con- 
denses. The change in volume is shown by the equation 

4H(solid) + 2 = 2H 2 (liquid). 

The gas which disappears is oxygen in the proportion of one gram 
molecule for each 4 grm. of hydrogen. The amount of available 
hydrogen in coals varies from 3 to 5 per cent, so that on a gram 
sample there would be on an average 0.04 grm. of hydrogen which 
would unite with 0.01 grm. molecule of oxygen causing a correction 
of 5 calories — a negligible amount except as it may be considered 
as balancing other minor errors such as that due to the oxidation 
of nitrogen. With petroleum the correction will be about three 
times as great as with coal. 

13. Water Value of Calorimeter. — When combustion occurs 
in a calorimeter there follows a rise in the temperature of both 
the water and of the calorimeter vessel. It is necessary to find 
how many calories are required to heat the metal parts of the 
calorimeter one degree and when this has been accomplished 
the value is translated for convenience of calculation into grams 
of water and called the water value of the calorimeter. The 
water value is usually determined in three ways. The first is by 
calculation from the weight of the metal parts and their specific 
heats; the second is by the combustion of a pure substance, such 
as sugar, benzoic acid or naphthalene, whose heating value is 
known; and the third is by the addition to the calorimeter of a 
definite amount of hot water with the determination of the rise in 
temperature resulting. The first method is simple but of only 
approximate accuracy. The second method has the advantage 
of tending to compensate for any errors such as the oxidation of 
nitrogen in combustion and even errors in the thermometer in so 
far as these are constant for a series of combustions. The third 



HEATING VALUE OF COAL BY THE BOMB CALORIMETER 233 

method has the advantage of being an absolute one, but it will be 
found somewhat more difficult of application. 

First Method. — The first method requires simply that the 
weights of each of the several different materials contained in the 
bomb, the stirrer, the thermometer and the water-containing 
vessel be known. By multiplying these weights by the specific 
heats as given in the following table the number of calories is 
obtained directly. 

TABLE OF SPECIFIC HEATS * 

Sp. ht. 

Tool steel 0. 1087 

Gun steel 0.1114 

German silver . 094 

Platinum 0.032 

Lead 0.030 

Oxygen (constant vol.) . 157 

Brass 0.094 

Mercury 0.033 

Glass 0.19 

The inaccuracy of the method lies partly in the fact that it is 
not possible to determine the individual weights of each of these 
constituents — e.g., the mercury in the thermometer, and partly in 
the fact that not all of the materials thus weighed are heated in 
actual practice to the temperature indicated by the thermometer 
immersed in water. A large part of the thermometer is outside 
of the calorimeter, a part of the stirrer is constantly passing in and 
out, and the top of the calorimeter vessel although within the 
calorimeter is not in contact with the water. On the other hand 
there is some transfer of heat from the calorimeter vessel to its 
j ackets of which no account is taken . Fortunately all these errors 
are minor ones but the method can hardly be considered accurate 
within 3 per cent. 

Second Method. — The method of determining the water value of 
a calorimeter by the combustion of a substance of known heating 
value is the most commonly employed and the most reliable one. 
Sugar and benzoic acid are substances which are readily obtained 
in a state of purity and whose heating value has been determined 
by a number of independent observers. The U. S. Bureau of Stand- 
ards considers the following heating values to be the most reliable : 

1 Atwater and Snell, J. Am. Chem. Soc, 25, 694. 



234 GAS AND FUEL ANALYSIS 

Cane sugar 3945 calories per gram. 

Benzoic acid 6321 calories per gram. 

Camphor 9290 calories per gram. 

Naphthalene 9612 calories per gram. 

The values for naphthalene are not very concordant. The 
heating values per gram as given by different authorities are as 
follows : 

Berthelot 9692 calories per gram. 

Atwater 9628 calories per gram. 

Fischer & Wrede 9668 calories per gram. 

The recent work of Richards and Jesse 1 has shown that very 
special precautions are necessary for the complete combustion of 
volatile hydrocarbons, and it is probable that incomplete combus- 
tion is in part to blame for the disagreement in the values for 
naphthalene. 

The procedure in determining the water value is exactly the 
same as for the combustion of a fuel. A sufficient amount of the 
pure material is pressed into a pellet so that the heat evolved by its 
combustion will be 7000-8000 calories. This is placed in the 
bomb which is charged with oxygen, set in the calorimeter and 
fired, the temperature readings being made as usual. In the 
final calculations the unknown to be solved for is the mass of 
water equivalent to the calorimeter which has been heated. The 
difference between this value and the mass of water actually 
added gives the water value of the calorimeter. 

The method of conducting the combustion is the same as that 
for coal and should be recorded according to the form, § 8. The 
following example gives the method of calculation. 

Total heat evolved 

from benzoic acid 1 . 0856 X 6320 =6860 calories 

from iron wire 0.022 Xl600= 35 



6895 
Corrected rise in temperature 2 . 854° C. 
Heat absorbed by water 2000 X 2 . 854 = 5708 



Heat absorbed by calorimeter . 1187 calories 

1 187 
Water value = o~o ft = 415 

1 J. Am. Chem. Soc, 32, 268 (1910). 



HEATING VALUE OF COAL BY THE BOMB CALORIMETER 235 

The accuracy of this process is dependent first on the purity 
of the materials used as a standard. Samples of pure substances 
with certified heat value should be obtained from the Bureau 
of Standards. The accuracy is also affected by errors in the ther- 
mometer, errors due to oxidation of nitrogen, etc., but in this 
very fact lies one of the valuable points of the method. For if 
it be assumed that with a thermometer set at a given zero there 
is an error of 0.02° in a rise of three degrees and that there is a 
correction of 8 calories to be made with oxygen from a certain 
tank when a sample of sugar which gives a rise of 3°, is burned, 
and both of these corrections be neglected, it is evident that the 
water value obtained will be in error. But if this erroneous water 
value be used in the calculations of the heating value of a coal 
where the errors due to the thermometer and the oxidation of 
nitrogen are the same as in the combustion of sugar, and where the 
total rise in temperature is approximately the same, the erroneous 
water value will compensate for the errors on the coal test and the 
result of the coal test will be correct. 

Third Method. — The third method of determining the water 
value of a calorimeter requires that the instrument, set up as 
if for a combustion except that there is no water in the calor- 
imeter vessel, be allowed to stand in a room free from draughts 
and of quite constant temperature until all parts of the instru- 
ment have come to a uniform temperature which is correctly 
indicated by the thermometer. This requires several hours. 
The same mass of water as used in a regular determination is 
brought to a temperature approximately three degrees above 
or below that of the calorimeter and its temperature is accurately 
observed. This can best be done with the help of the thermom- 
eter taken from the calorimeter. If the calorimeter is at room 
temperature there is no danger of its changing within the few 
minutes necessary for the next steps. There is a decided danger 
of change of temperature of the water to be added, and to guard 
against error it should be kept in a flask as carefully insulated 
as possible and stirred so as to be of uniform temperature through- 
out. A vacuum flask or thermos bottle with a wide mouth is 
excellent. The temperature of the calorimeter and that of the 
water having been noted the lid of the calorimeter is removed, 
the water quickly poured in and the mixture stirred, while the 



236 GAS AND FUEL ANALYSIS 

usual temperature observations are made. Part of the heat 
given off by the water has been used to warm the calorimeter 
and part has been lost in radiation. The amount of heat re- 
ceived by the calorimeter divided by the rise in temperature 
gives the water value. This method gives values which are 
entirely independent of any errors due to impurity in sugar 
or benzoic acid or to oxidation of nitrogen, etc. If carefully 
carried out it is a satisfactory method. 

This method in its most accurate form imparts a definite 
amount of heat to the calorimeter electrically, instead of by 
added hot water. A fine wire coil of known resistance is placed 
in the calorimeter and an electric current of carefully measured 
voltage and amperage passed through it for a definite time. The 
method is used in research laboratories, but is hardly to be con- 
sidered a technical method, and is not described here in detail. 

14. Accuracy of Results. — It is the aim to determine by com- 
bustion in the bomb calorimeter the amount of heat which 
would be evolved by the combustion of a fuel in the outside air. 
This standard is not an absolute one, for not only will carbon 
be burned to carbon dioxide and hydrogen to water in an ordi- 
nary fire but also sulphur will be burned, in part to SO2 and in 
part to SO 3, and small amounts of nitrogen will be burned. In 
applying corrections to the figures obtained in the bomb calor- 
imeter it is customary to assume that all of the sulphur of the 
coal burns to SO3 in the bomb, and that all of it burns to SO2 
in the air, and that no nitrogen is oxidized on combustion of 
coal in air. The errors introduced by these assumptions are 
small and are usually neglected. The accuracy of the estimation 
of the amount of heat evolved by combustion in the bomb will 
depend on the accuracy with which the water value of the system 
is known, the care taken in making radiation corrections and the 
accuracy with which the rise in temperature is measured. This 
last usually involves the largest error. If the error is 0.01°, 
it will amount to about . 3 per cent, or 50 British thermal units. 
When care is taken in every detail and apparatus of superior 
quality is used the agreement between duplicate determinations 
will be closer than this but it is certainly not safe to claim a 
closer absolute accuracy since according to Jesse 1 the highest 

1 Jour. Ind. and Eng. Chem., 4, 748 (1912). 



HEATING VALUE OF COAL BY. THE BOMB CALORIMETER 237 

authorities differ by 0.25 per cent, as to the absolute heating 
value of sugar and benzoic acid. The Committee on Coal 
Analysis states that in their judgment results obtained by a 
single analyst should not differ more than . 3 per cent, and that 
results obtained by different analysts should not vary by over 
0.4 per cent. This high standard can only be attained when 
every precaution is observed. 

15. Gross and Net Heating Values. — The heating value of 
the fuel computed by the method given above gives the total 
heat developed when the water formed condenses to a liquid 
within the calorimeter. This gives the total amount of heat or 
the " gross" heat value. In most industrial operations the 
water escapes as steam, and if deduction is made for its latent 
heat, a lower "net" heating value is obtained. This "net" 
figure gives a closer approximation to the heat which is ordi- 
narily utilized, but it does not give it accurately, because an 
arbitrary assumption has been made as to the temperature 
of the escaping gases. It is customary to report the total 
heating value of the coal and allow the consumer to put such 
a factor on it as will indicate its relative efficiency for the 
purpose to which he intends to put it. The method of calcula- 
tion of net heating values is given in § 12 of Chapter VII on 
Heating Value of Gas. 



CHAPTER XVII 

HEATING VALUE OF COAL BY THE PARR CALORIMETER 
AND OTHER METHODS 

1. Introduction. — The preceding chapter was devoted to a 
discussion of the bomb calorimeter as the standard instrument 
for the determination of the heating value of coal. The present 
chapter will deal with other methods, such as combustion in 
stream of oxygen, combustion with chemicals like sodium per- 
oxide, and calculation of the heating value from the chemical 
composition of the coal. 

2. Combustion in a Stream of Oxygen. — Calorimeters of this 
type have become obsolete on account of difficulties of manipu- 
lation and sources of error. The temperature of the oxygen 
flowing in must be accurately measured and also the temperature 
of the gases flowing out, for correction must be made for the heat 
which these streams of gas carry. The great source of error is 
the incomplete combustion of the coal. With bituminous coals 
the smoke may frequently be seen issuing from the instrument 
and even with anthracite and coke, carbon monoxide may always 
be found in the escaping gases. Accurate results have been 
obtained with this type of calorimeter but only after laborious 
correction for the large number of errors. 

3. The Thompson Calorimeter. — A very crude form of calor- 
imeter which has also become obsolete was that of Lewis Thomp- 
son. He mixed powdered coal with potassium chlorate and 
nitrate, placed the mixture in a calorimeter vessel and fired the 
charge. The method and apparatus were crude throughout 
but the greatest source of error lay in the heat absorbed in the 
decomposition of the chlorate and nitrate. When coal burns 
under a boiler it unites with gaseous oxygen to form CO2 and H 2 0. 
Essentially the same result takes place in a bomb calorimeter. 
When, however, the oxygen is taken from one form of chemical 
combination and is made to combine with the coal to form a 
different compound, the result is not at all the same as that 

238 



HEATING VALUE OF COAL BY THE PARR CALORIMETER 239 



obtained in the combustion of the coal with gaseous oxygen and 

the corrections to be applied must be worked out with great care. 

Scheurer-Kestner 1 determined that if 15 per 

cent, was added to the heating value obtained 

with the Thompson calorimeter, the results 

never differed by more than 4 per cent, from 

those obtained by the Favre and Silverman 

calorimeter which burns the coal in a stream 

of oxygen. 




Hffll 



Fig. 46. — Parr calorimeter. 



Fig. 47.— Details of 
Parr calorimeter. 



4. The Parr Calorimeter. — Parr 2 proposed sodium peroxide as 
a chemical to be used in oxidizing coal in a calorimeter, worked 
out the corrections to be applied, and devised a very practical 

1 Bull. Soc Ind., Mulhouse, 506, 1888. 

2 Jour. Am. Chem. Soc, 22, 646 (1900). 
Jour. Am. Chem. Soc, 24, 167 (1902). 
Jour, Am. Chem. Soc, 29, 1606 (1907). 
The Chemical Engineer, 6, 253 (1907). 
/. Ind. and Eng. Chem., 1, 673 (1909). 



240 GAS AND FUEL ANALYSIS 

calorimeter. He writes the probable reactions in the calorimeter 
as follows: 

2Na 2 2 +C==Na 2 C0 3 +Na 2 
Na 2 2 +Na 2 0+4H+0 = 4NaOH. 

There is more heat evolved in each of these reactions than in the 
combustion of carbon and hydrogen with gaseous oxygen but 
fortunately the reduction factor is closely the same for both of 
them. The heat evolved by the combustion of carbon and hydro- 
gen in the Parr calorimeter multiplied by 0.73 gives the true heat 
value. Smaller corrections are to be made for the dissociation 
of the KCIO3 used, for the oxidation of sulphur, the combustion 
of the fuse wire, the fusion of the ash, and the hydroxyl or 
combined water present in coal. 

Since the oxygen is introduced as a solid and the Na 2 C0 3 and 
NaOH formed in the reaction are also solids, the bomb need not 
be made to resist high gas pressures but may be made of thin 
metal. 

The general arrangement of the calorimeter is shown in Fig. 
46 where B and C are two fiber buckets acting as heat insulators, 
A is the can for water, and D the combustion bomb which sits 
upon a cone F and is rotated by a belt running in the pulley P. 
The stirring is very effectively accomplished by the removable 
wings shown attached to the bomb which force the water down 
the annular space between the bomb and the shell E out of open- 
ings at the bottom and up again on the outside. 

Details of the bomb are shown in Fig. 47 where A is the brass 
shell closed at each end by a plate and gasket held in place by a 
screwed cap. The top plate forms the bottom of the stem B 
which carries in its center the insulated wire KJI of the firing 
circuit. The lower cap D together with the sleeve E forms an 
air chamber around the lower portion of the bomb which prevents 
too sudden cooling of the fused mass and thus allows time for 
completion of the reaction. 

5. Preparation of Parr Calorimeter. — The bomb must be 
thoroughly dry and the gaskets in good condition. It is best to 
dry the parts after each test- in an oven and to examine them 
carefully before putting them together. The lower cap C is 
fitted into place, the outer sleeve E screwed on and the plug 



HEATING VALUE OF COAL BY THE PARR CALORIMETER 241 

D screwed firmly down with the wrench provided. Water 
leaking into the bomb always spoils the determination and may 
cause an explosion. 

The coal is to be ground to pass a 100-mesh sieve in order that 
it may react rapidly with the peroxide. Anthracite coal, coke, 
semi-bituminous and eastern bituminous coals in which the 
moisture will not exceed 3 per cent, may be used in an air-dry 
condition. Other bituminous coals, lignites, peats, etc., must be 
dried at 105° C. before use to avoid the reaction between the 
hygroscopic moisture and the peroxide with evolution of heat in 
the calorimeter. The danger of change in the coal sample during 
the processes of drying and grinding is treated in Chapter XV on 
Chemical Analysis. 

It is necessary to secure very intimate mixture of the coal, the 
Na 2 02 and the KC10 3 added as an accelerator of combustion. 
Professor Parr recommends that 1 grm. of the dry and finely 
ground KCIO3 be weighed into the bomb first, and to that be 
added 0.5 grm. of the coal prepared as directed above and that 
the two be mixed by stirring with a glass rod. To this is added 
approximately 10 grm. of sodium peroxide which may be meas- 
uerd with sufficient accuracy in the scoop provided with the 
instrument. The contents of the bomb are next to be thoroughly 
mixed by shaking. If this were done after the regular top and 
firing wire were in place the firing wire would almost certainly 
become twisted and short circuited, so it is better to use the false 
top provided. It is well at the beginning of the shaking process 
to invert the cartridge and tap it sharply on the desk to dislodge 
any coal which may have stuck to the bottom. When the mixing 
is complete the bottom of the cartridge may be tapped lightly 
against the desk to dislodge any material sticking to the cap. 
The regular top to which about 4 in. of fine iron wire (32 or 
34 American gage) has been attached in a loop as shown at G 
of Fig. 47 is now placed carefully in position and screwed into 
place. Care should be taken after this has been adjusted, not to 
tip the bomb since the fine iron wires are easily crossed. The 
spring stirring clips may now be adjusted and the apparatus set 
up as shown in Fig. 46. 

The strength of the firing current will vary between 2 and 4 
amperes. It should be adjusted by trials in the open air until 

16 



242 GAS AND FUEL ANALYSIS 

the wire fuses promptly on closing the switch. Where electric 
current for ignition is not available another form of calorimeter 
head may be used which allows ignition by a hot wire slug dropped 
through the hollow stem. The specified dimensions of the slug 
for this purpose are 1 cm. long, and 2.5 mm. diameter. This 
gives a weight of a little over 0.3 grm. and involves a correction 
of about .022° F. 

6. Care of Sodium Peroxide. — Sodium peroxide is hygroscopic 
and absorbs moisture from the air, even when preserved in appar- 
ently well-stoppered bottles, forming Na 2 02.2H 2 0. The effect 
of this hydrate formation is illustrated by an experiment made by 
Professor Parr. He exposed 10 grm. of sodium peroxide on a 
watch glass in the laboratory for an hour and found that it had 
gained in weight nearly 0.5 grm. This peroxide when used in 
the calorimeter gave a rise in temperature higher by 0.194° than 
the pure peroxide. As the total correct rise of temperature in 
this experiment was only 2.180° it will be seen that the error was 
almost 9 per cent. 

The sodium peroxide should not only be pure and anhydrous 
but should also be in grains of the proper size. If the peroxide 
is too coarse the powdered coal tends to sift to the bottom of the 
bomb and escape combustion. If peroxide is too fine the reac- 
tion is sometimes very violent. The manufacturers of the calor- 
imeter furnish reliable peroxide in small hermetically sealed cans 
and also furnish a clamp-top fruit jar which is said to preserve the 
contents of a single can during its use. 

Sodium peroxide reacts at ordinary temperatures with all 
organic substances in presence of moisture with evolution of heat 
often sufficient to produce flame or explosion. Mixtures of 
sodium peroxide and coal which may have to be disposed of are 
not to be thrown into waste jars. They may be cautiously and 
slowly poured into a vessel containing considerable water which 
will absorb the heat and prevent violent reactions. Sodium 
peroxide causes bad burns on the skin. 

7. Operation of Parr Calorimeter. — The bomb prepared as 
above directed is placed in the calorimeter vessel and properly 
centered. Two thousand grams of water are then added to the 
calorimeter vessel. It is preferable that the temperature of the 
water should be about 2.0° C. below room temperature for the 



HEATING VALUE OF COAL BY THE PARR CALORIMETER 243 

radiation correction will be less under these conditions. The 
thermometer is adjusted and the bomb started to rotating at the 
rate of about 100 revolutions a minute. Temperatures are to 
be read at the end of each minute. Within two or three minutes 
the readings of the thermometer should become almost constant 
except for the regular and very slight change due to radiation. 
Should the thermometer rise irregularly and more rapidly than 
0.01 or 0.02° per minute during this preliminary period, there is 
probably a slight leak of water into the bomb. The operation 
must be at once stopped, the bomb taken out, wiped dry on the 
outside, opened and emptied. A leaky bomb is not only inac- 
curate but dangerous. After five readings at intervals of one 
minute each in the preliminary period have shown only this 
slight and regular change of temperature, ignition is effected by 
closing the switch on the cover of the instrument. The thermome- 
ter rises very rapidly owing to the thin walls of the bomb and 
the efficient stirring and usually reaches its maximum after two 
minutes. Nevertheless observations should be continued for at 
least eight minutes after ignition to allow corrections for radia- 
tion to be made. 

The bomb is then removed from the water, wiped dry and 
opened. There should be no trace of unburned carbon visible, 
nor any odor. The lower plug is removed and the fused cake in 
the bottom of the bomb knocked into a casserole containing 
about 500 c.c. of water. The bomb should also be placed in the 
water until all the fused peroxide has dissolved. It is then 
removed, rinsed out and dried. 

The solution in the casserole is to be tested for unburned car- 
bon. As an alkaline solution it contains black flakes of oxides of 
iron and copper. After acidification it becomes a clear yellow 
solution, with carbon as the only matter in suspension, the silicic 
acid remaining in solution in the large volume of water. If any 
unburned carbon is visible it should be filtered on a Monroe or 
Gooch crucible, dried and weighed. A correction of 8.1 calories 
must be made for each milligram of unburned carbon. This 
precaution should never be omitted by a beginner nor where 
accurate work is important. 

The corrected rise of temperature may be calculated according 
to the formulas given in Chapter XVI, but a simpler method will 



244 GAS AND FUEL ANALYSIS 

usually suffice since this calorimeter is not used where the greatest 
accuracy is required. It is sufficiently accurate to assume that 
the average change in temperature per minute during the final 
period represents also the change due to radiation for each minute 
during the combustion period. The errors involved in this 
assumption are small since the temperature in the combustion 
period rises to almost its full value in the first minute. The tem- 
perature at the end of the fourth minute after ignition, may be 
taken as the end of the combustion period and corrections as 
shown by the next four minutes' readings, applied to it. Cor- 
rections for potassium chlorate, sulphur, ash, etc., as given in 
the following section are to be deducted from this reading, 
the result being the corrected final temperature. 

The instrument as furnished by the makers has a standard 
water equivalent of 135 grm. The corrected rise in tempera- 
ture multiplied by 2135 and by the factor .73 and divided by the 
weight of the sample in grams gives the heat value in calories 
per gram. The figure may be converted into British thermal 
units per pound by multiplying it by 1.8. 

8. Corrections to be Applied with Parr Calorimeter. — Parr has 
worked out very carefully the correction to be applied and pub- 
lished his results in the journals cited as references at the com- 
mencement of this chapter. He has shown that the ratio of the 
heat evolved in the combustion of carbon and hydrogen with 
gaseous oxygen to that evolved on combustion with sodium 
peroxide is very closely represented by the factor 0.73. The 
KCIO3 used as an accelerator evolves an additional amount of 
heat. Similar corrections are required for ash, sulphur, fuse 
wire, and hydroxyl constituents of the coal. Since the calor- 
imeter is always furnished with a standard water value these 
corrections may be calculated in terms of temperature. Profes- 
sor Parr's latest corrections 1 are as follows, the charge being 
0.5 grm. coal, 10 grm. Na 2 2 and 1 grm. KCIO3. The corrections 
are to be subtracted from the observed rise in temperature. 

Each per cent, ash is multiplied by : . .0.00275° C. 

Each per cent, sulphur is multiplied by 0.005° C. 

Correction for heat reaction of KC10 3 (l.g.) is 0. 130° C. 

Heat of combustion of fuse wire (10 mg.) is 0.008° C. 

1 J. Ind. and Eng. Chem., 1, 673 (1909) 



HEATING VALUE OF COAL BY THE PARR CALORIMETER 245 

Heat brought in by hot ignition slug is 0.012 

Correction for water of composition in bituminous 

coals with over 30 per cent, volatile matter is 0.025° C. 

Correction factors for hydroxyl in other substances are as follows, 
when 0.5 grm. material is taken for combustion. 

Brown lignites 0.050° C. 

Wood 0.111 

Sugar . 145 

Benzoic acid . 124 

The water value of the calorimeter may be experimentally 
determined by direct weight of the various parts or by combustion 
of a pure substance as described in Chapter XVI. The latter 
method is not so satisfactory as it is with the bomb calorimeter, 
since it involves the use of the factor 0.73. Benzoic acid and 
sugar involve also the added correction for hydroxyl. 

It is difficult to get ignition of anthracite and coke without 
adding a small amount of some readily combustible substance 
such as benzoic acid. The heating value of benzoic acid is 6320 
calories per gram and in the Parr calorimeter 0.2 grm. will evolve 

7t=w calories plus the added calories due to its hydroxyl contents. 

Reducing this to a temperature basis it amounts to 0.811 + 0.050° 
C. =0.861° C. to be subtracted in case 0.2 grm. benzoic acid is 
used as an igniter. 

9. Accuracy of Parr Calorimeter. — The work of Professor Parr 
has shown definitely that accurate results may be obtained with 
this calorimeter, but it has also shown that this accuracy can be 
gained only by the observation of precautions and the use of 
corrections which deprive the process of much of the simplicity 
which formerly characterized it. Accurate results are dependent 
on the quality of the peroxide used, a point which must usually 
be taken on faith. The calculations involve a knowledge of the 
ash, sulphur, and volatile matter of the coal, and the application 
of corrections for these constituents. These points prevent the 
method from being a standard one as is combustion in the bomb 
calorimeter, but do not prevent it from being a useful commercial 
instrument where the highest accuracy is not required. 

10. Calculation of the Heating Value from Chemical Analysis — 
If an ultimate analysis is available, the heating value of a coal 



246 GAS AND FUEL ANALYSIS 

may be calculated with fair accuracy from the Dulong formula 
which is usually given as 

_ . .. 8080 C + 34460 (H-§) + 2500 S 
Calorific power = z-^ 

where C, H, O and S represent the respective percentages of 
these various elements shown by the analysis. This formula 
gives results in Calories per kilogram which when multiplied by 
1.8 are converted into British thermal units per pound. Tests 
of 57 coals made by the U. S. Geological Survey 1 show an average 
error of 87.5 calories in the calculated result and a maximum 
error of 312 calories. Inasmuch as it is much simpler to deter- 
mine the calorific value directly than to make an ultimate analy- 
sis, the value of this formula has come to lie largely in its confir- 
mation of the correctness of the ultimate analysis. 

A formula which would correlate proximate analysis and 
heating value would be much more useful, but on account of the 
variable composition of the volatile matter in different types of 
coal no general formula can be devised which will fit all cases. 
The combustible matter of coal from a given seam is, however, 
quite constant in composition and after its value has been experi- 
mentally determined this figure may be used with considerable 
accuracy as a basis for the calculation of the heating value of 
similar coals whose moisture and ash content are known. 

1 U. S. G. S., Professional Paper 48 (1906); Bulletin 382 (1909) p. 24. 



APPENDIX 



247 



TABLE I.— SATURATION PRESSURE OF WATER VAPOR 



From 0-50° C. in millimeters of mercury. 
Phys. (4), 31, 731 (1910). 



Scheel and Heuse, Ann. d. 



Temp. 


mm. Hg. 


Temp. 


mm. Hg. 





4.579 


26 


25.217 


1 


4.926 


27 


26.747 


2 


5.294 


28 


28.358 


3 


5.685 


29 


30.052 


4 


6.101 


30 


31.834 


5 


6.543 


31 


33 . 706 


6 


7.014 


32 


35.674 


7 


7.514 


33 


37.741 


8 


8.046 


34 


39.911 


9 


8.610 


35 


42.188 


10 


9.210 


36 


44.577 


11 


9.845 


37 


47.082 


12 


10.519 


38 


49.708 


13 


11.233 


39 


52.459 


14 


11.989 


40 


55.341 


15 


12 . 790 


41 


58.36 


16 


13.637 


42 


61.52 


17 


14.533 


43 


64.82 


18 


15.480 


44 


68.28 


19 


16.481 


45 


71.90 


20 


17.539 


46 


75.67 


21 


18.655 


47 


79.62 


22 


19.832 


48 


83.74 


23 


21.074 


49 


88.05 


24 


22.383 


50 


92.54 


25 


23.763 







248 



GAS AND FUEL ANALYSIS 



TABLE II.— REDUCTION OF GAS VOLUMES TO 0° AND 760 MM. 
MERCURY PRESSURE AND DRYNESS 

If the gas is already dry the reduction formula is 



V : 



1 + .00367 t 760 



where t is the temperature and h the barometric pressure corresponding to 
the volume V. 

If the gas is saturated with moisture there must be deducted from the 
oberved barometric reading the value e for the vapor pressure of water 
corresponding to the temperature t as given in Table I. The reduction 
formula then becomes 



V = 



1 + . 00367 t 760 



The following table gives the values for l+0.00367t for each degree 
from 0° to 50° C. 



t 


l+0.00367t 


t 


l+0.00367t 





1.00000 


26 


1.09542 


1 


1.00367 


27 


1.09909 


2 


1.00734 


28 


1 . 10276 


3 


1.01101 


29 


1 . 10643 


4 


1.01468 


30 


1.11010 


5 


1.01835 


31 


1.11377 


6 


1.02202 


32 


1.11744 


7 


1 . 02569 


33 


1.12111 


8 


1.02936 


34 


1 . 12478 


9 


1.03303 


35 


1 . 12845 


10 


1.03670 


36 


1.13212 


11 


1.04037 


37 


1.13579 


12 


1.04404 


38 


1 . 13946 


13 


1.04771 


39 


1.14313 


14 


1.05138 


40 • 


1 . 14680 


15 


1.05505 


41 


1 . 15047 


16 


1.05872 


42 


1.15414 


17 


1.06239 


43 


1 . 15781 


18 


1.06606 


44 


1.16148 


19 


1 . 06973 


45 


1.16515 


20 


1.07340 


46 


1 . 16882 


21 


1.07707 


47 


1 . 17249 


22 


1 . 08074 


48 


1.17616 


23 


1.08441 • 


49 


1 . 17983 


24 


1.08808 


50 


1 . 18350 


25 


1.09175 















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252 





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3 C 
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5 U 

a c 


3 O i-O O >0 O 

a O O i-i i-i <M 



253 



254 



GAS AND FUEL ANALYSIS 



TABLE V.— MEAN SPECIFIC HEATS OF GASES AT CONSTANT 

PRESSURE IN B.T.TJ. PER CUBIC FOOT AT 60° F. AND 30 IN. 

OF MERCURY CALCULATED FOR THE INTERVAL 

60° F.-T 



T, 

deg. F. 


Carbon dioxide 


Water vapor 


Nitrogen, oxygen and 
other diatomic gases 


200 


0.0237 


0.0220 


0.0174 


400 


. 0246 


0.0220 


0.0175 


600 


0.0253 


0.0221 


0.0177 


800 


0.0260 


0.0222 


0.0178 


1000 


. 0268 


. 0224 


0.0180 


1200 


. 0275 


0.0226 


0.0181 


1400 


0.0282 


0.0229 


0.0183 


1600 


0.C287 


. 0232 


0.0184 


1800 


0.0292 


. 0236 


0.0186 


2000 


0.0298 


0.0240 


0.0187 


2200 


. 0302 


0.0245 


0.0189 


2400 


. 0306 


0.0250 


0.0190 


2600 


0.0309 


0.0256 . 


0.0192 


2800 


0.0312 


0.0263 


0.0194 


3000 


0.0314 


0.0270 


0.0196 


3500 


0.0317 


0.0288 


0.0201 


4000 


0.0319 


0.0312 


0.0206 



TABLE VI.— MEAN SPECIFIC HEATS OF GASES AT CONSTANT 

PRESSURE IN B.T.U. PER POUND CALCULATED FOR 

THE INTERVAL 60° F.-T 



T 


Carbon dioxide 


Water vapor 


Nitrogen 


200° F. 


0.2067 


0.4653 


0.2365 


400° F. 


0.2143 


0.4657 


0.2386 


600° F. 


0.2216 


0.4673 


0.2407 


800° F. 


0.2285 


0.4698 


. 2428 


1000° F. 


0.2348 


0.4735 


0.2449 


1200° F. 


0.2406 


0.4782 


0.2470 


1400° F. 


0.2462 


0.4841 


0.2491 


1600° F. 


0.2512 


0.4910 


0.2512 


1800° F. 


0.2559 


. 4990 


0.2534 


2000° F. 


0.2601 


0.5081 


0.2555 


2200° F. 


0.2638 


0.5182 


0.2576 ' 


2400° F. 


0.2670 


. 5294 


0.2597 


2600° F. 


0.2698 


0.5420 


0.2618 


2800° F. 


• 0.2722 


0.5557 


0.2639 


3000° F. 


0.2742 


0.5702 


0.2660 


3500° F. 


0.2770 


0.6093 


0.2707 


4000° F. 


0.2790 


0.6599 


0.2755 



APPENDIX 



255 



TABLE VII.— VOLUME OF WATER VAPORS TAKEN UP BY ONE 

CUBIC FOOT OF AIR WHEN SATURATED AT VARIOUS 

TEMPERATURES 



Temperature 


Cubic feet of water vapor 


0°F. 


0.001 


12° F. 


0.002 


22° F. 


0.004 


32° F. 


0.006 


42° F. 


0.009 


52° F. 


0.013 


62° F. 


0.019 


72° F. 


0.027 


82° F. 


0.038 


92° F. 


0.053 


102° F. 


0.073 



TABLE VIII.— COMPARISON OF THE BAUME SCALE FOR 

LIQUIDS LIGHTER THAN WATER AND SPECIFIC 

GRAVITIES 



Degrees 


Specific 


Degrees 


Specific 


Degrees 


Specific 


Baume 


gravity 


Baume 


gravity 


Baume 


gravity 


10. 


1.0000 


36 


0.8433 


62 


0.7290 


11 


0.9929 


37 


0.8383 


63 


0.7253 


12 


0.9859 


38 


0.8333 


64 


0.7216 


13 


0.9790 


39 


0.8284 


65 


0.7179 


14 


0.9722 


40 


0.8235 


66 


0.7142 


15 


0.9655 


41 


0.8187 


67 


0.7106 


16 


0.9589 


42 


0.8139 


68 


. 7070 


17 


0.9523 


43 


. 8092 


69 


0.7035 


18 


0.9459 


44 


. 8045 


70 


0.7000 


19 


0.9395 


45 


0.8000 


71 


0.6965 


20 


0.9333 


46 


0.7954 


72 


0.6931 


21 


0.9271 


47 


0.7909 


73 


0.6897 


22 


0.9210 


48 


0.7865 


74 


0.6863 


23 


0.9150 


49 


0.7821 


75 


0.6829 


24 


0.9090 


50 


0.7777 


76 


0.6796 


25 


. 9032 


51 


0.7734 


77 


0.6763 


26 


0.8974 


52 


0.7692 


78 


0.6731 


27 


0.8917 


53 


0.7650 


79 


. 6699 


28 


0.8860 


54 


0.7608 


80 


. 6667 


29 


. 8805 


55 


0.7567 


81 


0.6635 


30 


0.8750 


56 


0.7526 


82 


0.6604 


31 


0.8695 


57 


0.7486 


83 


0.6573 


32 


0.8641 


58 


. 7446 


84 


0.6542 


33 


0.8588 


59 


0.7407 


85 


0.6512 


34 


0.8536 


60 


0.7368 


90 


0.6364 


35 


0.8484 


61 


0.7329 


95 


0.6222 



SUBJECT INDEX 

Page 

Absorption methods in gas analysis 28-40 

Acetylene, 29 

diffusion of " 80 

estimation of , . 81 

as inhibiting catalyzer 32 

solubility of in water 81 

Accuracy of coal analysis 212 

of coal sampling 191 

of explosion analysis 46 

of photometric work 131 

of technical gas analysis 27 

Air and chimney gases, volume 142 

determination of relative humidity 107 

impure affecting candle-power 131 

volume per pound of carbon in combustion 143 

and water vapor table of volumes 255 

Air-drying coal 195 

Alcohol as fuel, see liquid fuel. 

Alkaline pyrogallate, reagent for oxygen 33 

Ammonia, estimation in gas 169 

Argon group 86 

Arsenious oxide as reagent - 69 

Ash in coal 202 

accuracy of analysis 212 

Aspirators 5 

Atkinson method for sulphur in coal 207 

Average sample of gas 8 

Bar photometer 114 

Barium hydroxide as reagent for carbon dioxide 80 

Baume scale for liquids lighter than water, table 255 

Benzene, estimation 159 

Benzine as inhibiting catalyzer , . , 32 

Benzoic acid as standard in coal calorimetry 234 

Blast-furnace gases, sampling 136 

Bomb calorimeter, details ■'... 215 

manipulation. . 219 

see also heating value of coal 214 

Bray's No. 7 slit union burner 123 

British thermal unit denned 99 

Bromine water, reagent 29 

17 257 



258 SUBJECT INDEX 

Page. 

Bulbed gas burette for exact analysis 75 

Bunsen photometric screen 123 

Bunte's gas burette 65 

Burners, standard gas 122 

Butylene (iso), initial combustion temperature 54 

Calculation of candle-power 130 

explosion analysis 47 

heat lost in chimney gases 146 

heating value of coal 227 

heating value of gas 100 

heating value of gas from chemical composition Ill 

Calibration of bulbed gas burette 79 

gas burette 22 

wet gas meter 89 

Calorimeters for gas, requirements 87 

see heating value, 
see bomb, 
see Parr. 

Thompsons 238 

using oxygen under low pressure 238 

water value of 232 

Calory defined 99 

Candle, English parliamentary 115 

international 116 

balance 117 

Candle-power, accuracy of estimation 131 

bar photometer 114 

Bunsen screen 123 

calculations 130 

decreasing significance of 132 

details of test 128 

Edgerton Standard 121 

Elliot lamp 121 

equipment of photometer bench 126 

flicker photometer 126 

gas meter 126 

humidity of air 130 

impure air 131 

jet photometer 131 

Leeson star disc 123 

Lummer-Brodhun photometric screen 123 

method of rating 113 

of illuminating gas 113 

photometer room 130 

saturating water of meter 126 

secondary standards 121 



SUBJECT INDEX 259 

Page 

Candle-power, setting consumption of gas 129 

solubility of illuminants 126 

standard gas burners 122 

standard lights 115 

table photometer 114 

types of photometer 114 

units of intensity 115 

use of Hefner lamp 117 

use of pentane lamp 120 

use of standard candles 116 

Capillary tube preventing explosion 50 

Carbon dioxide 28 

determination of 80 

formation of 139 

table of specific heats 254 

Carbon monoxide causing change in blood 82 

in chimney gas 141 

combustion with copper oxide 54 

and cuprous chloride 35 

determination of 35 

estimation of by cuprous chloride 82 

estimation of by iodine pentoxide 82 

evolved from pyrogallate solution 33 

explosion analysis 48 

fractional combustion with pallodinised asbestos ... 52 

hydrogan and methane simultaneous explosion 48 

incomplete absorption 35 

initial combustion temperature 54 

quiet combustion with oxygen 51 

Carbon, total, in coal 209 

Carbonates in coal ash 202 

Carbonic acid, see carbon dioxide. 
Carbonic oxide, see carbon monoxide. 

Carburetted water gas , 159 

Caustic soda, reagent 28 

Chemical analysis of coal, see coal analysis . 

Chemical analysis and heating value of coal 245 

Chemical composition of gas and heating value Ill 

Chimney gas 139 

calculation for loss of heat in 145 

carbon monoxide in 145 

change in composition in contact with water 7 

effect of hydrogen of coal on composition 140 

interpretation of analysis 147 

loss of heat in 147 

loss of heat due to moisture 144 

volume 143 









260 SUBJECT INDEX 

Page 

Chimney gases, and volume of air 142 

Chollar tubes 67 

Clinkering properties of ash 203 

Coal analysis 193 

accuracy 212 

air-drying 195 

ash 202 

deterioration of samples 198 

fixed carbon 203 

grinding sample ' 196 

hydrogen 209 

method of reporting 211 

moisture 198 

nitrogen 210 

oxygen 211 

phosphorus 211 

preliminary examination of sample 194 

preserving sample 198 

sulphur 204 

total carbon 209 

ultimate analysis 209 

volatile matter 200 

Coal, ash in 202 

briquetting sample for bomb calorimeter 218 

changes on air-drying 195 

changes after mining 189 

chemical analysis 193 

combined water in 145 

difference in composition of lump and fine 182 

fixed carbon in 203 

Coal gas 159 

chemical composition 157 

see illuminating gas. 

Coal, grinding 197 

gross and net heating values 237 

heating value of, see heating value . 

moisture in 198 

precautions in crushing 187 

proximate analysis 193 

Coal sampling 181 

accuracy 189 

a scoopful as a sample 184 

difference in composition of lump and fine coal 182 

from cars. 186 

from wagons • 186 

influence of lumps of slate 185 

in the mine 186 



SUBJECT INDEX 261 

Page 

Coal sampling, mixing 188 

picking a sample 186 

preparation of sample 187 

preservation of sample • 188 

reliability of samples 192 

size of sample 184, 191 

sulphur in 204 

substance 211 

tar as fuel, eee liquid fuel. 

ultimate analysis 209 

variations in results 191 

volatile matter 200 

washing 213 

Coke oven gas 159 

Colloidal palladium as reagent for hydrogen 38 

Combustion with copper oxide, accuracy of 86 

fractional with copper oxide 54 

fractional- with palladinised asbestos 51 

methods in gas analysis 41 

quiet of air and gas 49 

tube for copper oxide 55 

Contrast photometer 125 

Conversion factors for heating value of gas 100 

Copper oxide, fractional combustion with. 54 

quartz combustion tube 55 

Corrections for temperature and pressure of gas 71, 90 

Corrections for temperature and pressure, tables 248-252 

Cubic-foot bottle 89 

Cubic foot of water, weight of 89 

Cuprous chloride acid solution 35 

ammoniacal solution 36 

and carbon monoxide 34 

preservation of 35 

as reagent for carbon monoxide 82 

as reagent for oxygen 34 

regeneration 36 

Cyanogen compounds in gas 170 

Diffusion, errors due to 80 

prevention of 80 

Dulong formula 246 

Edgerton Standard lamp. 121 

Electrical precipitation of suspended particles 137 

Elliot lamp 121 

Eschka method for sulphur in coal , 204, 205 

Ethane, analysis by combustion 57 



262 SUBJECT INDEX 

Pack 

Ether as inhibiting catalyzer 32 

Ethylene 29 

initial combustion temperature 54 

as inhibiting catalyzer 29 

Exact gas analysis 70 

absorption methods 80 

bulbed burette for 75 

burette for 73 

manipulation of burette 77 

Excess oxygen over explosion requirements 48 

Explosive ratios 45, 84 

Explosion analysis, accuracy 46 

apparatus 41 

manipulation 44 

Explosion methods in gas analysis 41 

for hydrogen 46 

for methane 46 

Explosion, not prevented by capillary tube 50, 53 

Explosion pipette 41 

screen 43 

Explosion, simultaneous of hydrogen and methane 46 

simultaneous of hydrogen and methane and carbon mon- 
oxide 48 

Filtering media for solid particles in gas 136 

Fixed carbon in coal analysis 203 

Flash point of oils 180 

Flicker photometer 126 

Form of record of gas analysis 59 

heating value of gas 100 

Formation of producer gas 419 

Fractional combustion with copper oxide 54 

palladinised asbestos 51 

Fuels, liquid see liquid fuels. 

Fuming sulphuric acid, reagent 29 

Gas analysis, absorption methods 28-40 

accuracy of technical 27 

apparatus — Allen-Moyer modification 64 

Bunte's 65 

Chollar's • 67 

Orsat's 62 

Schlosing and Rollands 61 

various types 61 

calibration of burette 22, 79 

carbon dioxide 28, 80 

carbon monoxide 34, 82 



SUBJECT INDEX 263 

Page 

Gas, Analysis, combustion methods 41 

corrections for temperature and pressure 71 

details of manipulations 25 

drawing sample into burette 18 

exact methods 70 

exact methods, manipulation of burette 77 

by explosion, calculations 47 

by explosion, explosive ratio 45 

by explosion, hydrogen 46 

by explosion, manipulation 44 

explosion methods 41 

explosion, methane and hydrogen 46 

by explosion, oxidation of nitrogen 45 

form of record 59 

by fractional combustion with copper oxide 54 

by fractional combustion with palladinised asbestos. ... 51 

the gas burette 16 

gas pipettes 24 

general methods 14 

general scheme 38 

hydrogen • 83 

manipulation * 19 

manipulation of burette 24 

measurement of volume. 21 

methane 85 

nitrogen 58 

defines 81 

order of absorptions 39 

oxygen 30, 82 

by quiet combustion of oxygen and gas 49 

reduction of volume to standard conditions 72 

saturating burette water 18 

transferring gas from holder, see also under individual 

gases 19 

unsaturated hydrocarbons 28, 81 

wiring rubber connections 19 

Gas burette, calibration 22, 79 

bulbed for exact gas analysis 75 

with compensator for temperature and pressure 73 

description 15 

for exact gas analysis 73 

for exact analysis, manipulation 78 

manipulation, standard. 25 

see gas analysis. 

Gas burners, standard 122 

Gns calorimeters 87 

adjusting for a test 97 






264 SUBJECT INDEX 

Page ' 

Gas calorimeters, automatic Ill 

control of water 91 

Doherty's 110 

Graefe's 110 

Hempel's 110 

Junkers 92 

measurement of water heated 92 

Parr's 110 

recording Ill 

thermometers, see heating value of gas 91 

Gas, calculated heating value Ill 

candle power of 113 

candle power of, see candle power. 

estimation of suspended particles 133 

estimation of suspended tar and water 137 

heating value of, see heating value. 

holder for samples ' 12 

holder, transferring gas from 20 

illuminating, see illuminating gas. 

influence of bends in main on suspended particles 134 

main, point of sampling 135 

mains, distribution of suspended particles in cross section 133 

mains, influence of bends 134 

mean velocity in cross section of main 134 

meter for candle-power determinations 126 

wet 88 

wet, calibration 89 

natural, see natural gas 156 

percentage used for heating and lighting 132 

pipettes 24 

producer 149 

producer, efficiency : 155 

producer, see producer gas. 

sampling apparatus 9 

sampling, filters for solid particles 136 

sampling, see sampling gas. 

samples, shipment of 13 

sampling tanks, saturation of water 8 

specific gravity of 171 

suspended particles in 134 

table of specific heats 254 

velocity in sampling tube 135 

volume, corrections for temperature and pressure 90 

volume measurement, errors. . : 103 

volumes, tables of reduction 248-252 

Gases, change in volume in combustion 139 

from chimneys 139 



SUBJECT INDEX 265 

Page 

Gases, solubility in water 6 

Gasoline from natural gas 172 

Grinding coal samples 196 

Gross heating value of gas , 101 

Gross heating value of coal 237 

Heating value of coal, accuracy of results 236 

the bomb calorimeter 214 

calculated from chemical analysis 245 

in calorimeters using low-pressure oxygen 238 

in calorimeter using chlorate and nitrate 238 

corrections for combustion of iron wire 231 

corrections for oxidation of sulphur 230 

corrections for oxidation of nitrogen 229 

details of bomb calorimeter 215 

gross and net heating values 237 

manipulation of bomb calorimeter 219 

by Parr calorimeter 238 

Parr calorimeter details 242 

preparation of sample 218 

radiation correction 223 

reduction to constant pressure 231 

sample of record 227 

thermometer corrections 223 

thermometers 218 

water value of calorimeter 232 

Heat lost in chimney gases 143, 145, 147 

Heating value of gas 87 

accuracy of determination of 102 

calibration of meter 89 

calculated from chemical composition Ill 

calculation of results 99 

continuous flow calorimeters 87 

control of water 91 

corrections for temperature and pressure 71 

corrections for unsaturated air 106 

conversion factors 100 

corrections to observed heat to get total heat value 107 

description of test 98 

Doherty's calorimeter . 110 

errors due to sensible heat in combustion gases . . 104 

errors due to uncondensed water vapor 104 

errors in determining mass of water heated 104 

errors in temperature measurement 103 

errors in registration of gas volume 103 

form of record 100 

Graefe calorimeter 110 









266 SUBJECT INDEX 

Page 

Heating value of gas, gross value 101 

Hempel's calorimeter 110 

Junkers' calorimeter 92 

loss of heat by radiation 107 

measurement of mass of water 91 

measurement of temperature 91 

meter used 88 

method of reporting 100 

net value 101 

non-continuous calorimeters 110 

Parr calorimeter 110 

preliminaries of test 95 

recording calorimeters Ill 

saturating water in meter 98 

total accuracy 107 

Heating value of liquid fuels 175 

pure materials used in calorimetry 234 

Hefner lamp 117 

Hefner unit of light 116 

Humidity of air affecting candle-power 130 

determination 107 

relative, tables 252, 253 

Hydrochloric acid, removal of from gases 80 

Hydrogen absorption by palladium 36 

accuracy of estimation affected by explosive ratio 84 

carbon monoxide and methane, simultaneous explosion. ... 48 

in coal 209 

in coal affecting composition of chimney gas 140 

combustion with copper oxide 54 

comparison of methods for determination of 84 

combustion with oxygen 84 

determination of, by palladous chloride 37 

estimation of 83 

explosion analysis 46, 84 

error in estimation due to oxides of nitrogen 84 

fractional combustion with palladinized asbestos 51 

initial combustion temperature 54 

and methane by explosion 46 

and palladium, inhibiting catalyzers 36 

quiet combustion with air 49 

Hydrogen sulphide arsenious acid as reagent 69 

in illuminating gas 161 

as inhibiting catalyzer 32 

with carbon dioxide. . . 28 

removal of from gases 80 

Hydrosulphite as reagent of oxygen 34 

Hydrometer, Baume, for liquids lighter than water, table 255 



SUBJECT INDEX 267 

Page 

Illuminating gas 156 

benzene 159 

candle power of 113 

change in composition in contact with water 7 

chemical composition " 157 

estimation of ammonia 169 

estimation of cyanogen compounds 170 

estimation of suspended tar and naphthalene 166 

hydrogen sulphide in 161 

naphthalene estimation 164 

sampling 156 

scheme of analysis 157 

specific gravity of 171 

total sulphur compounds in 162 

typical analyses 158 

Illuminants, solubility of 126 

Incomplete combustion in chimney gases 141 

Inhibiting catalyzers for oxygen and phosphorous 32 

Initial combustioo temperatures of various gases 54 

International candle 116 

Iodine pentoxide as reagent for carbon monoxide 82 

Iron, heat of combustion 231 

Jet photometers 131 

Junkers' gas calorimeter 92 

Junkers' calorimeter for liquid fuels 177 

Junkers' recording calorimeter Ill 

Kjehldahl method for nitrogen in coal 210 

Leeson star disc 123 

Liquid fuels 174 

flash point 180 

heating value , 175 

Junkers' calorimeter for 177 

moisture 178 

proximate analysis of 179 

sampling 174 

specific gravity 178 

suspended solids in 179 

Lubricant for stopcocks 17 

Lummer-Brodhun contrast photometer 125 

photometric screen : . '. 123 

Measurement of gas volume 21 

Meter for candle-power determinations 126 

Meter, wet gas 88 



268 SUBJECT INDEX 

Page , 

Methane, accuracy of estimation affected by explosive ratio 85 

carbon monoxide and hydrogen, simultaneous explosion. ... 48 

combustion with copper oxide 54 

estimation of, by explosion . . . 85 

error in estimation due to oxides of nitrogen 85 

explosion analysis : 46, 85 

and hydrogen by explosion 46 

initial combustion temperature 54 

quiet combustion with air 49 

Metropolitan No. 2 burner 123 

Mine sampling of coal 186 

Moisture in air, see humidity. 

in coal 198 

in coal, accuracy of analysis 212 

in gas, calculation for 72 

in liquid fuels 178 

in tar 179 

Naphthalene estimation in purified gas 164 

estimation in tar 167 

estimation in purified gas 165 

as standard in coal calorimetry 234 

Natural gas 156 

analysis 172 

gasoline vapors in 173 

typical analyses 173 

Net heating value of coal 237 

of gas 101 

Nitrogen in gas analysis 58, 86 

in coal 210 

oxidation in bomb calorimeter 230 

table of specific heats 254 

defines 29 

Estimation of mean composition 81 

Orsat apparatus 62 

Oven for air-drying coal samples 196 

Oxides of nitrogen formed in explosion 44 

formed in combustion 51 

Oxidation of nitrogen, error caused by 45 

causing error in estimation of hydrogen 84 

Oxygen, always present 31 

analysis of commercial 32 

in coal 211 

concentrated and phosphorus 32 

determination of by alkaline pyrogallate 33 

determination of by phosphorus 30 



SUBJECT INDEX 269 

Page 

Oxygen, estimation by explosion with hydrogen 34 

estimation by metallic copper 34 

estimation of by phosphorus 82 

in excess of explosion requirements 48 

and phosphorus, inhibiting catalyzers 32 

and phosphorus at low temperatures 31 

by pyrogallate solution 33 

sodium hydrosulphite as reagent 34 

table of specific heats 254 

Palladinised asbestos 51 

Palladinised copper oxide for fractional combustion 54 

Palladium, colloidal as reagent for hydrogen 38 

and hydrogen, inhibiting catalyzers 36 

as reagent for hydrogen 36 

Palladous chloride as reagent for hydrogen 36 

Parr calorimeter 238 

accuracy 245 

corrections 244 

for heating value of liquid fuels 176 

operation 242 

preparation 240 

Pentane, analysis by combustion 57 

Pentane lamp 120 

Permanganate as reagent for reducing gases 80 

Peroxide calorimeter 239 

Peroxide 242 

method for sulphur in coal ■ 206 

Petroleum compounds, flash point 180 

moisture in 178 

see also liquid fuels 174 

Phosphorus in coal 211 

as indicator of absence of unsaturated hydrocarbons. 29, 31, 81 

inhibiting catalyzers 30 

and oxygen, inhibiting catalyzers 32 

and oxygen at low temperatures 31 

to be protected from light 30 

Phosphorus, reagent for oxygen 30, 82 

Photometer, bar type 114 

bench and equipment 126 

room 130 

table type 114 

Photometric units 115 

Photometry, see candle-power. 

Pintsch gas 29 

Pipette for explosion analysis 41 

Pipettes, gas 24 



270 SUBJECT INDEX 

Page 

Portable gas analysis apparatus 61-69 

Pressure of gas, corrections for 71 

Pressure of water vapor, table 247 

Producer gas analysis 151 

calculation of volume 153 

efficiency of producer 155 

formation 149 

heating value 153 

interpretation of analysis 152 

sampling 151 

sensible heat in 154 

typical analyses 150 

Propylene, initial combustion temperature 54 

Proximate analysis of coal 193 

Proximate analysis of liquid fuels 179 

Psychrometer 107 

Pyrites, separation 213 

Pyrogallol, evolution of carbon monoxide 33 

Pyrogallol, reagent for oxygen 33, 82 

Quartz combustion tube for copper oxide 55 

Quartz combustion tube with platinum spiral 49 

Radiation corrections in calorimetry 223 

Dickinson formula 228 

Regnault-Pfaundler formula 224 

Radiation loss in gas calorimeter 107 

Reduction of gas volumes to 0° and 760 mm. table 248 

Reduction of gas volumes to 60° F. and 30 inches, table 249-251 

Regnault-Pfaundler formula for radiation corrections 225 

Rubber connections, danger of in gas analysis 19 

Sampling blast furnace gas 136 

crude illuminating gas for naphthalene 166 

coal 181 

see also, coal sampling. 

gas, apparatus 9 

aspirators 5 

collecting a representative instantaneous sample 11 

collection of an average sample 8 

continuous apparatus 10 

difficulties 1 

errors due to solubility 7 

from main • 135 

illuminating 156 

liquid fuels 174 

materials for sampling tubes 2 



SUBJECT INDEX 271 

Page 

Sampling, method 3 

multiple sampling tube 3 

problem of fair sample 1 

producer, gas 151 

shipment of samples . 13 

solubility of gases in water 6 

storing the sample 11 

tube, proper velocity of gas 135 

Saturating burette water with gas 18 

water in gas meter 98 

Saturation of water in gas sampling tanks 8 

pressure of water vapor, table 247 

Slate as cause of error in coal sampling 185 

separation 213 

Sling psychrometer 107 

Sodium hydrosulphite as reagent for oxygen 34 

Sodium hydroxide, reagent 28 

Sodium peroxide, care of 242 

Solubility of gases in water 6 

Specific gravity compared with the Baume scale for liquids lighter than 

water, table 255 

of gas 171 

of liquid fuels 178 

Specific heat of materials used in calorimeters 233 

of gases, table of 254 

Standard gas burners 122 

Standard conditions for gas 90 

Standard light 115 

Stopcocks, care of 17 

Storage of gases 11 

Sugar as standard in coal calorimetry 234 

Sugg D burner 122 

F burner 122 

Sulphates in coal ash 202 

Sulphur in coal 204 

accuracy of analysis 212 

Eschka method 205 

peroxide method 206 

Atkinson method 207 

Parr's photometric method 208 

Sulphur compounds in illuminating gas 162 

Sulphur dioxide with carbon dioxide 28 

removal of from gases 80 

Sulphur, oxidation in bomb calorimeter 230 

Sulphuretted hydrogen, see hydrogen sulphide. 

Sulphuric acid, fuming as reagent 29 






272 SUBJECT INDEX 

Page 

Suspended particles in gas 133 

electrical precipitation 137 

filtering medium 136 

point of sampling 135 

Suspended solids in liquid fuels 179 

Suspended tar and water particles in gas 137 

Table photometer 114 

Tar as fuel, see liquid fuel 174 

estimation of naphthalene in 167 

in illuminating gas, estimation 166 

moisture in 179 

particles suspended in gas 137 

suspended particles in gas main 134 

Temperature of gas, corrections for 71 

of initial combustion of various gases 54 

measurement, errors 103 

Thermometer corrections for calorimetry 223 

for calorimetry 218 

wet and dry bulb 108 

Thompson calorimeter 238 

Tubes for sampling gases 2 

Ultimate analysis of coal 209 

accuracy 213 

Unsaturated hydrocarbons 28 

absence of, shown by phosphorus 29, 81 

estimation of 81 

estimation of mean composition 81 

separation 81 

Variation in coal samples, see coal sampling. 

Velocity, varying in cross-section of gas main 134 

Volatile matter in coal, accuracy of analysis 212 

Volatile matter in coal 200 

Volume of gases, tables for reduction to standard conditions 248-252 

Volume of producer gas 153 

Water, combined in coal 145 

Water gas, chemical composition 158 

Water value of calorimeter, determination of 232 

by direct weight of parts 233 

by combustion of pure substances 234 

by method of mixtures 235 

electrically 236 

Water saturated with air, composition of the gases 7 



SUBJECT INDEX 273 

Page 

Water vapor, table of saturation pressures 247 

table of specific heats 254 

table of volume for one cubic foot of air 255 

uncondensed in determining heat value of gas 104 

weight per cubic foot of saturated air 105 

weight of a liter at various temperatures 221 

weight per cubic foot 89 

Wet and dry bulb thermometers 108 

Wet gas meter. 88 

Wiring rubber connections 19 

Wiring stopper into burette 74 



INDEX OF AUTHORITIES CITED 

Page 

Allen and Jacobs 178 

Allen and Mc-yer 64 

American Chemical Society, see Committe on Coal Analysis. 

American Gas Institute 103, 116 

American Gas Institute, see Committee on Calorimetry. 

Atkinson 207 

Atwater 215 

Atwater and Snell 233 

Badger, see Hillebrand. 

Bailey 184, 185, 187, 196 

Barker 204 

Bartlett, see Gill. 

Berthelot 33, 214 

Blauvelt 136 

Bleier 75 

Brady ......" 136 

Brodhun, see Lummer. 

Bunsen 45, 85, 123, 171 

Bunsen and Playfair 70 

Bunte 65, 160 

Burrell 172 

Bureau of Mines 174, 191, 195, 209, 210, 211 

Bureau of Standards 106, 116, 221,. 223 

Campbell 16, 42, 54 

Campbell and Hart 36 

Chollar 67 

Cheney 215 

Church 179 

Coleman and Smith 164 

Committee on Calorimetry 88, 92, 104, 107, 110 

Committee on Coal Analysis 195, 198, 199, 200, 201, 202, 204, 207 

Committee on Photometry 130 

Coquillion 49 

Cottrell 137 

Davis, see Fieldner. 

Dennis and Hopkins 50, 85, 159 

Dickinson 228 

Drehschmidt 162 

Doherty , HO 

Doyere , 70 

Earnshaw 81, HI 

Eschka 204 

274 



AUTHOR INDEX 275 

Page 

Favre and Silverman 239 

Fernald and Smith 150 

Fieldner and Davis 200 

Franzen 34 

Gas Referees 90, 116, 120, 122 

Gill 42, 45 

Gill and Bartlett 83 

Graefe 110 

Haber and Oechelhauser 160 

Harbeck and Lunge 161 

Harding 162 

Harcourt 120 

Hart, see Campbell. 
Hartman, see Paal. 

Heath ■. 205 

Hempel 24, 36, 38, 42, 49, 51, 53, 71, 73, 110, 159, 214 

Hillebrand and Badger 198 

Hinman 45 

Heuse, see Scheel. 

Holmes 186 

Hopkins, see Dennis. 

International Photometric Commission 132 

Jacobs, see Allen. 

Jaeger 54, 86 

Jenkins 162 

Jesse 236 

Jesse, see Richards. 

Jones 35 

Junkers 88 

Kinnicutt and Sanford 82 

Klumpp 131 

Kroeker 209 

Ktister 164 

Lavoisier 70 

Le Chatelier, see Mallard. 

Leeson 123 

Lord 213 

Lummer and Brodhun 123 

Lunge : 161 

McCarthy, see Dennis. 

Mahler 215 

Mallard and Le Chatelier 143 

Morton 159 

Morton, see Pennock. 
Mover, see Allen. 

Mueller 170 

Nesmjelow 53 



276 AUTHOR INDEX 

Page 

Nicloux 82 

Noyes and Shepherd 48 

Oechelhaliser, see Haber. 

Orsat 34, 62 

Ovitz, see Porter. 

Paal and Hartmann 37 

Parr 110, 176, 189, 198, 200, 202, 206, 208, 209, 215, 231, 239, 244 

Pennock and Morton 206 

Petterson 73 

•Pfaundler 224 

Playfair, see Bunsen. 

Pope 192 

Porter 195 

Porter and Ovitz 189 

Ramsburg 161 

Regnault 224 

Regnault and Reiset 70 

Reiset, see Regnault. 

Richards and Jesse 175, 223, 234 

Rolland, see Schlosing. 

Rutten 165 

Sanford, see Kinnicutt. 

Scheel and Heuse 247 

Scheurer-Kestner 239 

Schilling 171 

Schlosing and Rolland 61 

Shepherd, see Noyes. 
Silverman, see Favre. 

Small 33 

Smith, C. D., see Fernald. 
Smith, see Coleman. 
Snell, see At water. 

Somermeier 230 

Stevenson 215 

Sundstrom 206 

Thompson 238 

Tutwiler 162 

U. S. Geological Survey 173, 246 

U. S. Weather Bureau 107 

White 51, 73, 84, 166 

White and Campbell 16, 42 

Winkler • . 51 






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